Sounds like usde-qt.exe is bugged, and produced an invalid wallet.dat file. Hope you have previous backups ... if not, contact the developers directly would be my suggestion.
That can happen?!
Its a program. Programs are (normally) bugged. So yeah, it can happen. But before panicking, contact the developers, they might have a fix in the works or some sage advise
I got my original wallet back by right clicking my usde folder, clicking properties, previous version tab and rolled back to the date when I deleted the original wallet and I got it. Now I'm scared to back up my wallet and I'm scared my local wallet might get hacked, so I'm basically screwed.