Crap, seems that somewhere between SDLMame 0117 and 0122 (I suspect 0121), launching games through applescript has broken. An apple script command run in Script Editor:

do shell script “/Applications/MAME/mame0122 /Applications/MAME/roms/game.zip”

is no longer equivalent to

/Applications/MAME/mame0122 /Applications/MAME/roms/frogger.zip

run in the terminal.

For now I suggest sticking with SDLMame 0116 or using MAME OS X with EMUlaunch.