2002 Grand Prix runs great until it will not move and engine will not rev.

You said the car won't move when you put it in drive .. what happens when you try to accelerate .. does the engine cough or sputter ? If nothing happens (no increase in engine speed) than open the hood and have someone observe the throttle movement when you step on the gas (only when the trouble occurs ) . I suspect it's the throttle position sensor or MAF (mass airflow sensor) .. If your handy with tools try the throttle position sensor first (easy to change and about $30 on ebay) Sorry not to be more specific but you did not mention if your CEL light (check engine light) came on ... if it did than many good auto stores will read the code and tell you the number ... I suspect you will find the code to be "P107"