Just before I came out to Chicago I bought an iPhone 3G. In the UK this is on the O2 network and in the US the iPhone operates on the AT&T network. However, when the 3G signal from AT&T gets sufficiently weak it seems that the iPhone loses the signal and then will reconnect to the T-Mobile network. This is what happened to me on Tuesday when I noticed that the phone was rebooting almost every minute. I tried all sorts to get fix it including doing a complete factory reset, thus wiping out all my contacts and music that I’d carefully prepared before coming away:-(

It turns out that I needn’t have bothered with any of this. The workaround is to simply turn off the 3G mode which is fine if you’re roaming out of the UK as the network data charges are astronomical (£6/MB). Turning off 3G and then doing a manual search for network provider usually allows you to connect back to AT&T. Just remember to re-enable 3G when you’re back in the UK.

Update: Forgot to include the link where I found the workaround:

http://discussions.apple.com/thread.jspa?threadID=1671274&tstart=465