There is a tool that can be used to attempt to recover .fbr files that are reported as corrupted, which is available for download here.
To use it:
- Make a backup copy of the corrupt FBR file.
- Extract the FBRChecker tool and run FBRChecker.exe
- Select the corrupt FBR file and click 'Check'
- If you see a message saying that the file can be recovered, click 'Recover'.