Update - Blackra1n - yes it works with 3.1.2

All of you planning to update to 3.1.2 with a iphone 3G, 3G which is factory unlocked can now use Blackra1n which is quick and the easiest possible way to jailbreak, however it is buggy and if you do want to make it work follow below with the links. Most people are complaning that once you use blackra1n they are getting stuck with the Itunes connect logo and then Itunes will automatically ask you to restore. This is a video which worked for me and its taken me a day and staying up all night to figure it out. Do it at your own risk. { watch the video first and REMEMBER what to press at the right time :-) }

How to Jailbreak Your iPhone, iPod Using BlackRa1n [Windows]
http://www.iclarified.com/entry/index.php?enid=5527

Video for the blackra1n Fix
http://modmyi.com/forums/other-methods/688448-blackra1n-iphone-3g-fix.html

Good luck