Time for a massive update: MAME 0.126u3. Due to a change internally with the way memory regions are handled, a large percentage of all files in the project needed to be updated.
There's been a regression test against the change already, so we should be beyond crashing problems. But it is possible that some games may be missing sound due to mismatched sound regions. If you hear anything funky, please report it to MAMETesters so that we can get the problems ironed out in time for u4.