You already know that greenpois0n who makes untethered jailbreak for iOS 4.2.1 has been released, you have tutorial for Mac OS X here, but I don't recommend you to test it because for now it doesn't work properly for many people. Pod2G was asked when the Windows version of greenpois0n will be available and he said that fixing the issues for the Mac OS X version is a priority. The Windows version should be available today if the Mac version is fixed, but if not, we should see it released this weekend. This version of greenpois0n can be run over a tethered jailbreak made with redsn0w, but not over an untethered one made with Jailbreak Monte, so be very careful. If you have an untethered jailbreak made with Jailbreak Monte, then you must first restore and only then jailbreak with the new greenpois0n.
Those from the Chronic Dev Team hastened the release even 2 days ago pod2g said that the solution is not yet 100% ready. We can all see the result of rushing the release, a non-functional solution available only for Mac, that is, a regular release for the Chronic Dev Team.
