I kinda remember this issue being mentioned before, but a search turns up nothing.
Have you tried messing around with the frameskip and throttling in MAME? (F8-F12 keys IIRC, but it's been years since I messed with this stuff)
There are also options for THROTTLE, SYNC TO REFRESH and WAIT FOR VERTICAL SYNC in MAME.ini
(names might be off, like I said, it's been years)
I loves me some CarnEvil.