3g Iphone and charger overheating? Please help

I bought two new 16gb 3g iphones yesterday.

I plugged in both iphones and noticed after about 10minutes, my iphone and charger(with the charger being significantly more warmer) became hot while my roomate's iphone didnt change temperature.

Trying diferent pieces(Power Converter, USB Wire and then USB and Power Converter) yielded the same results: regardless of which peice combination I used with my iphone, it came hot while my roomate's iphone and charger didnt change temperature. Therefore I think it has something to do with my actual iphone and not with the USB cable and converter.

Anyone know what this could possibly be?
Is this a valid concern to bring up with the Apple Store?

thanks!!!

it could not hurt to contact them and let them know what the situation is. see what they say.. and far and what it could be.. i have no clue, the phone has only been out 2 days so it is hard to tell. you might have to wait a while and see if other people are having similar problems