Doing some testing for using AHK with MAME and I can't get MAME to respond to any hotkeys! I stripped a script down to the simplest possible:
6::Send,1
This works in notepad, pressing "6" gives a "1", but in MAME I can load up a game, press "5" for a coin and if I press "6" to start nothing happens. If I press the "1" key it will start, but the alias key "6" never works.