Porsche Cayenne not starting at gas stations

(double post to get more traffic)

Strange thing happened.
Drives great no problems.
She gets gas and at the pump it won't start, but it is turning over fine, battery ok...no spark I guess.
Jumped and starts.
Take it to dealer they run codes, etc, have it overnight, always starts...send it out as "ok."
Drive it for 300-400 miles over several weeks, sits a lot (becasue she's worried about getting stuck) and it is 100% ok...no problems.
Goes in for the next tank of gas fill up, and exact same thing happens again!
Guy at service station gets it to start by pumping th egas pedal as cranking the motor over, and it starts.
Service station keeps car overnight...again no problems.

I seem to remember that when the car gets filled with gas it triggers some computer thing to calculate mileages and oil change intervals, etc....could the "signal" from getting gas be tripping something in the engine management system to prevent starting?

Thanks.