Reports have been coming in of some white iPhone 3GS becoming discolored after overheating. Apple has acknowledged the problem as partially true but only when 3rd party cases are involved.

Many had speculated that due to the iPhone 3GS’ faster CPU, that overheating would occur when using processor intensive app which is partially true. The main culprit is the combination of the backing becoming warm when the CPU is taxed and the use of a third party case. The heat causes the case to become warped and in some instances, fuse bits of it to the iPhone’s plastic exterior causing the discoloration. The obvious solution would be to stop using a 3rd party case with your iPhone.

“After numerous calls to Apple technical service and maintenance of contact with a level 3 (engineer) the problem seems to come not from a hot 3GS but contact with some covers! This was evident by ourselves on a device with a small sticker (a warning not to listen to music too loud) remained stuck, part of the hull below remained white. A simple solution to the problem is to clean the back of the iPhone with alcohol, tested by myself I can confirm that it works and reassure you it is safe for your precious.”

Via: TUAW