Are you running command line based or 32-bit MAME? Do you have the same issue when you run MAME outside of Mala or do your games run normally? Do you have any other unnecessary applications or processes running in the background? I had some issues (unrelated) that were resolved by creating a batch file that killed the explorer.exe process, then launched the mala.exe. To reload Windows, I set Mala to launch explorer.exe on exit. If MAME runs as advertised outside of Mala, maybe this solution would work for you, too?
On your other issue, I'd be willing to bet it is related to your first issue. Make sure everything works properly outside of Mala first.