Me too. It just started today. I've been using the latest leaked OS on my Bold 9900 and Torch 9810 on T Mobile, and as soon as it picks up WiFi from my house, it reboots and will keep rebooting when it turns on ONLY of the sim card is in. I can use both phones on WiFi when the sim card isn't in them, without rebooting. But as soon as I put the sim card in, it reboots when connecting to WiFi. I got a new sim card today, but it hasn't fixed anything. This is really irritating!
did anyone solve this problem - i had the same problem starting Aug 6th with a T-Mobile US 9900, and after a day fault finding with T-Mobile and then RIM they said it was a hardware fault with the 9900 and replaced it - i have now had the new phone for over a week and no problems so far - i now see other people had the same problem on the same dates, so that makes me think it was not a hardware problem - at least my replacement 9900 looks cleaner than my old phone...