Hi Clay
I just imported your database and I didn't have any problems (although I didn't have the media files, but I doubt that would cause a problem with tags). I think this was a bug in an earlier version. Can you go in the menu to Mnemosyne => About Mnemosyne and verify you're running the latest version 2.4.1? If not, upgrading may help
If you're still having problems send me another email