I had got iphone 3GS Beta with 3.1 modem firmware. My friend did update to 4.2 and also teether jailbreak. Now as soon as he finished jailbreak it. It went to recovery mode and always give USB+itune logo, looks it needs kick from recovery to operation mode. He now said he is waiting for small softwares for 4.2 which can help it in few days! Also itune reuiqres it restore but since it is jailbroken and i don't want to restore it.