I have a 3GS with new bootrom running 4.2.1 (do not have SHSH for any other iOS). I had a tethered redsn0w jailbreak, and when greenpois0n came out i tried running the jailbreak over it because i saw some people had success. that didnt work, so i put my iphone in recovery mode, then restored to the original 4.2.1, which failed like it should, then put it in DFU mode and restored the custom 4.2.1 firmware from pwnagetool. after that i ran redsn0w again, had the phone up and running, installed apps, restored from backup. then the next time i looked at my phone it was "off". it was actually in DFU mode again some how. I tried doing a tetherd boot in redsn0w, and it goes to restart, shows the white screen like it is supposed to, then the 2nd time redsn0w says its rebooting, the screen just gets brighter and stays at the white screen and does nothing. if i reboot my phone it goes in DFU mode, i cannot get it to go in recovery mode either, and i tried running all the options in redsn0w, and restoring both the custom and original apple 4.2.1 firmwares and they fail. tinyumbrella doesnt see my i phone, and every other program that kicks it from dfu mode is for 4.1. i have a mac laptop that i am trying everything on. anyone think of anything that i havent tried that might work?