On Apple's iPhone discussion boards, people are complaining about a bug in iPhone OS 3.1.2 that causes the iPhone to search for service at random times. According to the 3.1.2, Searching for Service thread on the forums, people are blaming the problem on the iPhone OS because users are seeing the same problem on AT&T in the U.S. and on Rogers Wireless and Telus in Canada.
According to the thread, there is no indication that the iPhone 3GS is affected, since so far the complaints focus on the iPhone 3G. Both new and replacement iPhone 3G units have suffered from the same problem.
The only fix for the problem so far is to reboot the iPhone.
Have you experienced this bug? What model iPhone were you using? Let us know in the comments.