My first Xfire (vin series 9xxx as I recall) had this problem. Two suggestions:

1) After running the a/c, park the vehicle and verify that you have water dripping from the condensate line on to your driveway. If not, the condensate line is blocked and that's your problem.

2) If #1 doesn't solve the issue, then your recirculation valve is stuck in the closed (recirculation) position. You can verify this by setting the fan on it's lowest setting with the engine off and hitting the recirculation switch. If you don't hear the sound of the valve (slight clicking noise) switching between the open and closed position, the valve is stuck or inoperative.

One of the above should solve your problem. (Good luck with the dealer!)