MAME4droid: Infinate lives anyone?

An easy method to activate the cheat system has been posted by Seleuco, though the problem will likely be fixed soon in an upcoming build.  In the meantime, simply create a folder in sdcard/Roms/Mame4all called cheat or  cheats.  ('cheat' worked for me.)  Then move the installed cheat.dat into it. Start MAME4droid, load a game with cheats enabled, call up the Mame menu and navigate to cheats, then enable the cheats of your choice.   Tested and working!