Hi there.
I found something interresting with mama:
I have a rom called Mortal Kombat in a zip file.
If I name the file MortalKombat.zip mame does not run at all.
If I name the file MK.zip mame says: Ther are files missing.
If I name the file mk.zip, the game runs fine!!!!
Perhaps this helps with other not working games.