Hi,
Ive only just registered on the site but have owned a crossfire roadster from new back in 2005.
I had a similar problem last year with my car, it would start fine but then just cut out for no reason. very inconvinient when driving.
it turned out to be a sensor for the exhaust fumes.
the sensor reads what gases are produced and cuts the engine out if it thinks it can damage itself.
In the end the sensor cost me £8 and a local mechanic from a mercedes fitted it for me.
hope that helps?