As we all know so well by now, the iPhone 3GS's processor runs a lot faster than the 3G model, though in actuality the previous handset's processor is capable of similar speeds. It was simply turned down, presumably to save on battery power and to reduce heat to surrounding components.

It seems this might have been an astute move, since Apple's forums have been lighting up with reports of iPhone 3GS models overheating to the point of discolouring the casing and even becoming too hot to hold against the ear during calls.

The overheating apparently does the device's operation no good, either, with reports of poor performance and charging difficulties as the handset runs hot.

Apple has responded quite quickly, however, and put much of the trouble down to the recent spate of hot weather. This response doesn't sound as though there's any fix coming, and puts the onus back on users to ensure they only operate the handset in environments that comply with Apple's ideal operating circumstances.

"Operate iPhone 3G and iPhone 3GS in a place where the temperature is between 0º and 35º C (32º to 95º F)," is the official advice, which goes on to say that functionality is likely to be reduced when, "Using certain applications in hot conditions or direct sunlight for long periods of time, such as GPS tracking in a car on a sunny day or listening to music while in direct sunlight."

Many of the complaints insist the overheating is taking place under normal usage, however, suggesting Apple could potentially be facing similar problems to those that have dogged Microsoft with the Xbox 360.