I had this problem, and I think it's a problem with the catver/dats... I ended up manually swapping them out.
I can't test right now, but that sounds like the problem... You know how every so often, they change the 'parent' rom and swap around which roms are 'the best'...
In other words, I don't think it's a mamewah issue, I think it's a 'mame support files' issue.