iPhone Atlas has already covered a number of complaints from iPhone users about iPhone OS 2.2.1.
Frequently, faulty Wi-Fi connections were the source of these complaints. Recently, that problem has resurfaced, and one user is linking the Wi-Fi problems to heat generated by the iPhone and its battery.
A discussion in the Apple forum describes a problem in which some iPhones are randomly dropping Wi-Fi signals, then failing to reconnect to any network for a period of time.
Many people think that the problem is caused by the iPhone overheating, and some go so far as to place their iPhone into a refrigerator to speed up the cooling process. (We don't suggest that you do the same; refrigerating your iPhone could cause water damage and void your warranty.) We recommend letting the iPhone cool at room temperature for 30 to 60 minutes, or until cool to the touch.
Apple Discussions user ScottieWil goes a step further and actually opened his iPhone to apply a nitrogen stick directly to the relevant chip. His Wi-Fi immediately returned to working order. ScottieWil researched the problem further and said in one of his posts:
I have now found the common factor in my Wi-Fi working and not working...its charge level of the battery. If the cell is under 50 percent, Wi-Fi just works...if it's above, it has problems. If the charge level is 90 percent or more, and I try to use Wi-Fi, the phone can reboot with(out) warning.
This, as I said before, may be the cell not being able to provide the current demand of the phone.
He also suggested that the iPhone's battery is very sensitive to temperature, which explains why Wi-Fi would work temporarily when the phone was cool, but not later, after the phone heated up.
If the tips above fail to resolve the problem, some people on the same discussion thread are reporting that AppleCare is replacing iPhones experiencing this heating problem. However, Apple is doing so only after the iPhone is examined at a local Apple store.
If you or someone you know has experienced this problem, let us know in the comments.