Error 507 simply means that there is no OS or firmware found upon booting of the phone. Thihs happens on failed Software update or corrupted phone memory.
You can attempt repair on it by following the instruction here.
Please be sure first that you have installed Blackberry Desktop Manager;
Download then install BB Desktop Manager.
and a firmware or OS for your 9300, depending on your network provider:
Just be sure to select the correct model number and network provider to download.
then check if you have existing Software on your computer
Start by going to your Control Panel and then Add and Remove Programs (in XP) or Programs and Features (in Vista) and remove any BlackBerry device software currently installed on the computer. Reboot the computer. With your desktop manager closed and your BlackBerry unplugged, install that OS on your computer, then reboot the computer.
After your computer has rebooted, plug your BlackBerry in and you can try using the BlackBerry Desktop Manager to load the OS on your phone, but in this case, you may find it easier to use the AppLoader file. You can find this under C:\Program Files\Common Files\Research In Motion\Apploader. To reduce the chance of any problems, you might also want to look through this folder for the Vendor.xml file and delete it first. After you've deleted the Vendor.xml file, double click on apploader.exe. This will open up the apploader which will load the device software onto your phone.
Uploading the OS to your device takes time, so be sure to be patient and never unplug the blackberry even though it may seem to hang on the screen. Let it finish its job until it says it is done. Unplugging it prematurely may render your phone useless.
Hope this helps you. Thank you for using Fixya.