I was also experiencing problems with the sound in Mame/Mamewah. The sound would break/stutter in seeming simple games like Pac-man and Galaga. However, the same games didn't have a problem in Mame32.
I did a careful comparison of the 2 ini files and there were a couple of seemingly minor differences. When I changed the settings in Mame.ini to be exactly the same as those in Mame32 (picture, sound, everything). All was well again.
However, seeing as you have said you have already done that, I'm at a bit of a loss. Perhaps you may have missed one? I know that I found that settings in the mame32 ini file were not in the same order as those in mame.ini. Took a bit of scrolling, but I got there in the end and no more sound issues.