2002 Mazda Protege5 electrical issue??

I have a 2002 Mazda Protege5 that has had the same problem on and off for the past
two years.  If I am driving down the road, going 80 mph, turn on the lights - the car
dies.  It will crank right up.  Sometimes it dies when  I come to a stop.  Basically I
loose all power when I am turn on multiple electrical items (radio, lights, roll down
windows).  We've put way too much money into this car and frankly I want to set her
on fire.  She's bee to six different mechanics ... nobody can figure out the problem.  
She will run great for a day or two .. even a month or two .. then the problem is back.  
Sometimes she won't crank - but roll starts just fine.  In the past two years I have:  
replaced the control arms, new alternator, new battery, new oxygen sensor (both), new
coil pack, new motor mount, new timing belt, new water pump, new gasket set, new
spark plugs, had the fuel system checked and they only found a crooked o ring -
replaced it.

I am at my wits end with this car!!!!