I cant get defender to work either.
On the desktop I can press F3 and this is configured as the system reset button so defender reloads out of config mode.
You mentioned that you can copy a .cfg file for the game.
Unfortunately the versions of Mame I run on my desktop use .ini files (which are easy to reconfigure) I can't find any .cfg files to copy across
Which version do you use?
And have you had any more luck.