If an error log exists, it would be under \AppData\ErrorLog.dat if you're using the portable edition. Otherwise ErrorLog.dat will be in C:\users\<username>\AppData\Roaming\MusicBee. If it's not in \Roaming, look in Local. I can't remember which is used by the installed edition.
You might also try launching MB as Administrator. Right-click on MusicBee.exe and click on 'Run as administrator."