Argh! I've been using MAME .118u2 with the hi score patch (compiled myself using Mr. Do!'s excellent tutorial) but Mappy and Super Pac-man were giving me errors when I tried launching them. Apparently there is a known issue with the mappy.c driver in MAME .118u2 which both games use to run. This is completely unacceptable.
I decided to recompile MAME using version .119u3 with the hi score patch hoping that the games would work again and I was right - they worked! Unfortunately, Galaga is no longer playable. This is doubly unacceptable. Galaga is on the short list of must-have games for an arcade cabinet. I'm missing a file called 51xx.bin which was added in the Galaga file starting with MAME .119u3 so tonight I have to recompile yet again and go back to MAME .119u2. What a pain - hopefully I can get everything working!
I'm not sure why I posted this... maybe this information will help someone else out there. I don't know.