Modem problem every time i try using the apple usb modem to connect in my mac mini the computer freezes and asks me to restart?

There could be several reasons why your Mac may not recognize a USB product. Here are some possible solutions:

1. Check the USB port: Make sure the USB port is not damaged and is clean. Try plugging the USB product into a different USB port on your Mac.
2. Check the USB product: The USB product may be defective or damaged. Try plugging the USB product into a different computer to see if it works. If it does not work on any computer, the product may be defective and you may need to replace it.
3. Check the USB cable: The USB cable connecting the USB product to your Mac may be faulty. Try using a different USB cable to connect the USB product to your Mac.
4. Restart your Mac: Sometimes a simple restart can resolve USB connectivity issues. Restart your Mac and then try plugging in the USB product again.
5. Update your Mac: Make sure your Mac is running the latest version of macOS. Go to the Apple menu and click on "System Preferences," then click on "Software Update" to check for any available updates.
6. Reset the SMC: The System Management Controller (SMC) controls many hardware functions on your Mac, including USB connectivity. Resetting the SMC may help resolve USB connectivity issues. The steps to reset the SMC vary depending on the model of your Mac, so it's best to check Apple's support website for specific instructions.

If none of these solutions work, it may be best to contact the manufacturer of the USB product for further assistance, or take your Mac to an authorized Apple service provider for further diagnosis.

Back up your profile data using Time Machine. Restore your computer to factory settings using the disc that came with your Mac and transfer settings from backup.

If you are running thought bootcamp for the windows partition have you installed the boot camp drivers?

If not, put in your OS X instalation CD and the auto run should open the instaler for these, jsut follow that thought restart the mac and see if it works then.

Try hitting your capslock key (which will light up) or command-tab (which will switch between applications) to see if the keyboard and computer are still responding when this happens. If so, it sounds like the mouse or the USB port it is connected to may unfortunately be failing. 
Also, try connecting the mouse to another USB port as others have suggested, either on the keyboard or computer itself, as this will help you determine if the failure is in the mouse or port.

restart your pc press del key in your keyboard,
go to setup usb settings disable usb 2.0 setting

Laptop or portable connecting via USB? "See iPod not recognized when connected to Windows laptop over USB for more information. Your computer doesn't meet iPod system requirements Make sure that your computer meets the system requirements to use iPod for Windows. Your iPod displays an exclamation point folder or sad iPod icon, or doesn't appear in iTunes or My Computer If your iPod displays a folder with an exclamation point icon or a sad (unhappy) iPod icon on its screen, or if your iPod doesn't appear in iTunes or My Computer, follow these instructions to resolve the issue. Your iPod isn't formatted for Windows iPod for Windows Software only recognizes iPod for Windows. You cannot use iPod for Macintosh with a Windows PC. To see which platform your iPod is formatted for, follow these instructions. Your iPod isn't connected to a high-power USB port If you're connecting an iPod, iPod mini, or iPod shuffle to your Windows computer, make sure that you're connecting it to a high-power USB 2.0 port on your computer (not a low-power one such as the USB port on your keyboard or bus-powered USB hub). Typically, USB 2.0 high-power ports are located directly on your computer. Try connecting your iPod to another USB port on the computer (or to a self-powered USB 2.0 hub that's connected to a high-power USB 2.0 port on your computer) if the computer still doesn't recognize your iPod. Alternatively, if your computer has a FireWire connection, try using that instead. If you're connecting an iPod, iPod mini, or iPod shuffle to a Windows laptop computer through USB, connect the laptop to a power outlet before connecting your iPod. You're not using a WHQL-certified IEEE 1394 card If you have a FireWire (IEEE 1394) card installed in your computer and are using it to connect your iPod, make sure that the card is Windows Hardware Quality Labs (WHQL) certified. If it isn't, your iPod may not be recognized, or you may not be able to send music to the iPod. If you're not sure about your card's WHQL certification, check the inbox material that came with your FireWire card or contact the card's manufacturer. You can view a list of WHQL-certified cards on the Windows Hardware Compatibility List website. To view this: Go to the Windows Hardware Compatibility List website. Enter All Products in the ""Search for"" field. From the Product Categories pop-up menu, choose 1394 Controller. Click the Search Now button. Note: Windows XP information is not listed on the initial search screen, but is listed when you click on an individual card. You can also check the list of recommended FireWire and USB cards that have been tested by Apple with iPod and Windows XP. (Apple sells FireWire cards that are compatible with iPod at the Apple Store.) To rule out an issue with your FireWire card, try connecting a different FireWire device to the card to see if your computer recognizes it. Your connections aren't secure Make sure that there i

Maybe radical but this worked for me.
My computer-select ipod,Right click and format disc (fat 32)
Once refomatted plug in to computer and start Itunes.
Click on Restore to factory settings, At the end of that you will need to plug it briefly into an ac outlet.
Reconnect ti computer and start Itunes.
Sync with library.
This worked for me after trying everything else I could fine failed.

My error when I ran diagnostics said "one or more sync tests failed."

For Mac users "iPod does not appear in iPod Updater or iTunes in Mac OS X Under some circumstances, iPod appears in the Finder in Mac OS X, but does not appear in the iTunes Source list or does not appear in the iPod Updater. Symptom iPod's disk icon appears in the Finder, but it does not appear in the iTunes Source list or in the iPod Updater. Note: The iPod may appear in iTunes, but not in the iPod Updater. Important: If you are using iPod shuffle, you must have 10.2.8 or 10.3.4 or later to connect it to your Mac over USB. Other iPods require 10.3.4 or later Products affected Mac OS X iPod (5 GB) iPod (10 GB) iPod (touch wheel) iPod (dock connector) iPod mini - USB requires Mac OS X 10.3.4 or later. iPod mini (Second Generation) - USB requires Mac OS X 10.3.4 or later. iPod (Click Wheel) - USB requires Mac OS X 10.3.4 or later. iPod with color display (including iPod photo) iPod nano Solution iPod nano Certain models of single processor Power Macintosh G5 computers may show iPod nano mounted in the Finder but not recognized in iTunes. If this happens to you, try restarting your computer and Setting Energy Saver to highest performance and turn off hard disk sleep. If you have an iPod nano, but don't have a G5, then follow the other steps below. Mac OS X 10.4.x Perform an archive installation of Mac OS X10.4. Mac OS X 10.3.x Navigate to /System/Library/Extensions. Drag the iPodDriver.kext file to the Trash (you will be required to enter an administrator account password). Download and install the Mac OS X Combined Update 10.3.9. Restart the computer when prompted to do so by the installer. Connect the iPod. Mac OS X 10.2.8 and earlier To resolve this issue with earlier versions of Mac OS X, you'll need to delete one file and reinstall iTunes. Follow each of the steps below. Step 1 Delete the file using Terminal Warning: The steps below describe how to remove a file by entering commands in the Terminal application (located in the Utilities folder inside of the Applications folder). Users unfamiliar with Terminal and UNIX-like environments should proceed with caution. The entry of incorrect commands may result in data loss or unusable system software. Open Terminal (/Applications/Utilities). Type: sudo rm -R /System/Library/Extensions/iPodDriver.kext Press Return. Enter the administrator account password when prompted. Quit Terminal. Restart the computer (From the Apple menu, choose Restart). Step 2 Reinstall iTunes Download the latest version of iTunes from the iTunes download page. Install iTunes. Restart the computer after the installation has completed. Connect iPod. Step 3 Delete the iPod.plist file Remove the following file in the your home directory and launch the iPod updater again ~/Library/Preferences/com.apple.ipod.plist "

For Mac users "iPod does not appear in iPod Updater or iTunes in Mac OS X Under some circumstances, iPod appears in the Finder in Mac OS X, but does not appear in the iTunes Source list or does not appear in the iPod Updater. Symptom iPod's disk icon appears in the Finder, but it does not appear in the iTunes Source list or in the iPod Updater. Note: The iPod may appear in iTunes, but not in the iPod Updater. Important: If you are using iPod shuffle, you must have 10.2.8 or 10.3.4 or later to connect it to your Mac over USB. Other iPods require 10.3.4 or later Products affected Mac OS X iPod (5 GB) iPod (10 GB) iPod (touch wheel) iPod (dock connector) iPod mini - USB requires Mac OS X 10.3.4 or later. iPod mini (Second Generation) - USB requires Mac OS X 10.3.4 or later. iPod (Click Wheel) - USB requires Mac OS X 10.3.4 or later. iPod with color display (including iPod photo) iPod nano Solution iPod nano Certain models of single processor Power Macintosh G5 computers may show iPod nano mounted in the Finder but not recognized in iTunes. If this happens to you, try restarting your computer and Setting Energy Saver to highest performance and turn off hard disk sleep. If you have an iPod nano, but don't have a G5, then follow the other steps below. Mac OS X 10.4.x Perform an archive installation of Mac OS X10.4. Mac OS X 10.3.x Navigate to /System/Library/Extensions. Drag the iPodDriver.kext file to the Trash (you will be required to enter an administrator account password). Download and install the Mac OS X Combined Update 10.3.9. Restart the computer when prompted to do so by the installer. Connect the iPod. Mac OS X 10.2.8 and earlier To resolve this issue with earlier versions of Mac OS X, you'll need to delete one file and reinstall iTunes. Follow each of the steps below. Step 1 Delete the file using Terminal Warning: The steps below describe how to remove a file by entering commands in the Terminal application (located in the Utilities folder inside of the Applications folder). Users unfamiliar with Terminal and UNIX-like environments should proceed with caution. The entry of incorrect commands may result in data loss or unusable system software. Open Terminal (/Applications/Utilities). Type: sudo rm -R /System/Library/Extensions/iPodDriver.kext Press Return. Enter the administrator account password when prompted. Quit Terminal. Restart the computer (From the Apple menu, choose Restart). Step 2 Reinstall iTunes Download the latest version of iTunes from the iTunes download page. Install iTunes. Restart the computer after the installation has completed. Connect iPod. Step 3 Delete the iPod.plist file Remove the following file in the your home directory and launch the iPod updater again ~/Library/Preferences/com.apple.ipod.plist "

For Mac users "iPod does not appear in iPod Updater or iTunes in Mac OS X Under some circumstances, iPod appears in the Finder in Mac OS X, but does not appear in the iTunes Source list or does not appear in the iPod Updater. Symptom iPod's disk icon appears in the Finder, but it does not appear in the iTunes Source list or in the iPod Updater. Note: The iPod may appear in iTunes, but not in the iPod Updater. Important: If you are using iPod shuffle, you must have 10.2.8 or 10.3.4 or later to connect it to your Mac over USB. Other iPods require 10.3.4 or later Products affected Mac OS X iPod (5 GB) iPod (10 GB) iPod (touch wheel) iPod (dock connector) iPod mini - USB requires Mac OS X 10.3.4 or later. iPod mini (Second Generation) - USB requires Mac OS X 10.3.4 or later. iPod (Click Wheel) - USB requires Mac OS X 10.3.4 or later. iPod with color display (including iPod photo) iPod nano Solution iPod nano Certain models of single processor Power Macintosh G5 computers may show iPod nano mounted in the Finder but not recognized in iTunes. If this happens to you, try restarting your computer and Setting Energy Saver to highest performance and turn off hard disk sleep. If you have an iPod nano, but don't have a G5, then follow the other steps below. Mac OS X 10.4.x Perform an archive installation of Mac OS X10.4. Mac OS X 10.3.x Navigate to /System/Library/Extensions. Drag the iPodDriver.kext file to the Trash (you will be required to enter an administrator account password). Download and install the Mac OS X Combined Update 10.3.9. Restart the computer when prompted to do so by the installer. Connect the iPod. Mac OS X 10.2.8 and earlier To resolve this issue with earlier versions of Mac OS X, you'll need to delete one file and reinstall iTunes. Follow each of the steps below. Step 1 Delete the file using Terminal Warning: The steps below describe how to remove a file by entering commands in the Terminal application (located in the Utilities folder inside of the Applications folder). Users unfamiliar with Terminal and UNIX-like environments should proceed with caution. The entry of incorrect commands may result in data loss or unusable system software. Open Terminal (/Applications/Utilities). Type: sudo rm -R /System/Library/Extensions/iPodDriver.kext Press Return. Enter the administrator account password when prompted. Quit Terminal. Restart the computer (From the Apple menu, choose Restart). Step 2 Reinstall iTunes Download the latest version of iTunes from the iTunes download page. Install iTunes. Restart the computer after the installation has completed. Connect iPod. Step 3 Delete the iPod.plist file Remove the following file in the your home directory and launch the iPod updater again ~/Library/Preferences/com.apple.ipod.plist "