Sorry to be slow to respond.  I don't hang out here much anymore...busy, busy.
Well, my next guess is you might have a corrupted database.
Try creating a new database, and plopping your movie into that.  If it works, you might have a bad sector on your hard drive.  You can run error checking against the drive to see if that fixes it, or you can install a firebird server and use a repair tool for the database.  From PVD, optimise MIGHT work, but doubtful...and it's likely to cause data loss as well.  Exporting the title and imdb urls into a file and importing them into the new database might be a good option...just run a mass update on all records.
Yah, my collection is a bit out of hand.  Database is just under 2GB.  Almost 9k movies, 130k people.  About 25% of people have a least one photo.  No screen shots.  Been pruning the worst of the worst to make space, but it's a slow process.