I think, thatīs not the problem and he just wrote it wrong.
I have my roms in the ROMS-subdirectory and I have the same effect as posted above. Black screen and retun to main-screen.
Some games run(1941-43,Asteroids,Vanguard...) but other (my favourits included) donīt run e.g. Bosconian, Phoenix, New Rally X.
I use a Ipaq 3850 with lots of memory(most Programs put on memory-card, so I have about 26MB program-memory free while MegaMameCe is running.) That canīt be the problem.