Best idea may be to download the Javaloader program and use it to do a complete wipe of the device, including the OS. Then, use the Application Loader in the Blackberry Desktop Manager to reinstall the OS. Then you can restore from backup. You can get all of the information on how to use it by opening a command prompt in the folder where you extract javaloader.exe to and typing javaloader/? The command you probably want is:
javaloader -usb wipe.
Once you start it, it only takes a few seconds for it to complete. You will most likely see the same error message, but you should be able to open up the Application Loader and reload the Blackberry OS.
I have included the file as a .zip attachment.