Does the position of the dimmer switch make a difference? It sounds like a dead short somewhere downstream of the headlight switch that's dropping the system voltage enough to kill the ignition. Try turning the headlights on with the engine stopped, and see if they go dim or flicker on and off.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!