I wanted to let everyone know I used Greenpois0n along with tinyumbrella to jailbreak iphone4. I now have 4.1 with a baseband of 01.59.00. Everything seemed to work just fine however it sit quite a long time in DFU mode during the process. It seemed to time out but I walked away from it and was patient. When I came back it had an error. I used tinyumbrella to kick it out of DFU and low and be hold 4.1 with 01.59.00. Everything tested and has been fine for a few days now. No crashes no errors but the process seemed long and almost as if it had gone bad. Just a warning be patient and ride it out. It will work.