I had the same problem for a while and I couldn't figure out what was wrong, I tried reinstalling the software and a few other things, but I later realized when you uninstall the software, the database is still saved and that message I believe means that the file is somehow corrupted. What you should do is unistall the software and then find the upperdeck folder, where mantis is in your programs folder and delete it. After that you should reinstall the software. You will have to reenter any UDE numbers that were in the system, so you will need to get any of those, but it should work fine after that.