car AC vent mount too cold for iPhone 4???

I put my iPhone 4 on one of those car mount that clips on the A/C vent. I have the AC on medium, after about 10 minutes the iPhone just turn itself off. And I can't turn it back on with the power button. I need to press and hold home and power together for about 10 sec for it to turn back on. This never happens with the 3G before on the same mount with even AC on high. The iPhone is cold when it happen but not too cold to handle. I see that the operating temperature is Operating temperature: 32° to 95° F (0° to 35° C) but I do not think that the AC in the car is that cold.

It happen twice already, so now I guess I just do not "MOUNT IT THAT WAY".