Scanner not working

Uninstall all of the software and then reinstall it. If still issues contact Brother tech support for assistance. They are really wonderful and will get you up and running. Your wifi is working so the router is not an issue. Check out your usb cable and try another one or a different usb port on computer.

How to get a MFC-8840/D/DN to scan to Windows 7 over the network or by USB:

First - Download the Windows Vista Full Driver & Software Package from Brother: Brother MFC-8840DN driver download page

Install the drivers using a custom install - pick only the Network scanning drivers, unless you want the other junk - no promises on how well the other stuff works.
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Alternatively, if connecting the MFC-8840DN to Windows 7 by USB, download the Printer and Scanner Driver for Local Connection. It is a separate download. Install only the Scanner driver.
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Once the Vista scanner driver is installed, you can test by running the built-in Windows 7 Scanner Wizard. Here are instructions on how to test.

As far as conversion to PDF, that will depend on the software. I am not sure if the Control Center or Paperport softwares work on Windows 7. I have not tried those. I have found that freeware STP will works fine.
Here is a link to the STP homepage.
Here is a link to how to use STP with the Brother MFC-8840DN

I have the same problem. It was working fine, then after not using it for a few weeks, all the sudden I couldn't scan. I'm hooked up wirelessly through my router. I can initiate a scan both from my PC and from the scanner itself, when initated from the scanner my PC responds and shows the progress bar, and the scanner actually scans. However for some reason no data is being sent back to the PC. And after a few minutes I get an error message saying that communication was lost (or something like that) error TW007. Yesterday I called into brother support and was on the phone for an hour and a half. they walked me through verifying connectivity, uninstalling and reinstalling the software and drivers, but to no avail. In the end we made no progress. I can print without a problem, and fax and photocopy. But for some reason it seems that the scanner is not transmitting the information back to the computer, even through the connection was established and the computer is waiting for the data.

Are you scanning from the PC, or are you scanning from the printer?

If the latter, the scanner is trying to send the document to a server software on the PC, which is probably not running; hence the "not connected" message.

Try acquiring a picture using Control Panel -> Scanners -> Acquire Image and see if it works. If it does, you must run (or reinstall) the Control Center software, and configure it as to where to store the Scan-to-File documents.

Was this function working fine before? When you choose Scan => To Email, what the device actually do is launch the scanning software and scan it and save to temporary folder THEN open your default OUTLOOK email account and creates a new mail with the scanned file attached to it. So it could be a scanning software error or low in memory since the process requires an amount of memory.

So you better try to Scan => To File and see if the scanning completes. If you have problem with it, then try to reinstall the program of your printer and scanner in one.

My guess is a driver problem. I'm assuming you can print to it, so you know the USB connection is good. And you can make a copy (I assume), so you know the scanner mechanism and its connection with the rest of the machine works.
The scanner driver is separate from the printer driver. It's entirely possible to install and use the printer without having loaded the scanner driver. Best bet is to unplug the unit from your computer, then uninstall it completely from Windows. There may be an Uninstall program listed under Brother in your Start menu...All Programs... Or go to Start...Settings...Control Panel (or however your version of Windows get there) and open your Scanners and Cameras folder. If you find the Brother machine in there, Select it and click Remove. Do the same in the Printers folder.
Don't plug your machine back in until you have reinstalled the drivers. Go to www.brother-usa.com, and in the Service & Support box on the right, click Downloads. That will take you to a page where you'll select Multi-Function as your Product Group, then the model.
You'll get two lists of links. Forget Manuals, look at Drivers on the right.
Under Type of Software, click ALL. Select your OS.
You'll get a list of drivers and utilities for your model. Select the Full Package. Brother makes you accept the Terms of Use, then starts the download.
Look for Setup.exe in the main directory, or you may need to browse folders labeled with different language abbreviations to find it.
Start the installation, and don't plug your USB cable in until the computer tells you to. it will install the printer first, then return to install the scanner. It may require you to restart Windows more than once. Sorry.
Once you've suffered through all that it should be fine.

Never mind. I went to http://welcome.solutions.brother.com/BSC/public/eu/eu_ot/en/model_top/colormfc/mfc210c_all.html?reg=eu&c=eu_ot&lang=en&prod=mfc210c_all and downloaded a program called "Brother Control Center"(version 2.4.2.) and now my scanner works just splendidly!

you need to make sure that the brother printer is et as the default printer

This printer requires the software for MAC 10... The link below will show method from MAC website.

http://support.apple.com/kb/HT2502

It is waiting for authentication. Set the username and password of the computer you are scanning to,on the scanner.