I had my first MSP for exactly 24 hours when it just shut down. I was going like 75 across a bridge (very flat) when it just turned off and the engine, oil, tranny, and abs lights came on. It had like 1/4 tank of the original gas from the dealer. Tried starting it periodically for over an hour while I waited for roadside assistance to show up and it never started.
The bastards at the dealership wanted to give me a rental car while they "fixed" it. But... uhhh.. NO. I freaked on them and they gave me a new one. Now I am glad I freaked... sounds like it is a somewhat common problem. Next time I go into that evil place I'll ask what they discovered, if anything, and post it here.
Not that any of this helps you fix your cars, just want you to know I shared your plight. I have had no problems with teh replacement so far...
Good luck
Vapor