Well, I've switched over to SDLMAME, and I still have sound issues. This time, it's just that everything is very crackly, but I haven't had it cut out on me...
what version of SDLMAME are you running and on what hardware?
I've found that as the hardware requirements of newer versions of MAME (since about .106) have steadily outstripped my supply of free/salvaged/junk PCs that I have used for my cabs.
If your hardware is on the aged side, I'd suggest trying an older version of SDLMAME, or alternatively AdvanceMAME.