I've been attempting to build a complete MAME 0.78 non-merged set from various other MAME sets I have laying about. It's been pretty seemless using RomCenter. One issue, though, is that at some point some of the WAV samples got renamed with a double extension. E.g. "explo3.wav" becomes "explo3.wav.wav". Annoyingly I've even had it where it's showed as green inside the set and won't show as yellow (Bad name) until I reload the rom path. Refreshing doesn't work.
This bug has affected me probably three times in the last week with this same set. It's happening after some combination of fixes. Hopefully my log file gives some clues.