I'm really happy for the many replies, but I'm still a bit confused about what will work, and what won't. I agree that exluding the whole extensions seems to be a risk, but if it's the only thing that will work, then it's ok in this situation.
I would rather exclude all files named STORE.FDB but since the box says "File (include full path)", then I guess it's not possible to just enter a filename without a path.
How do I check if the exception is working? Should I look at a log file on the client to see if it's skipping this file, and which log file would that be?