Hey guys got a friend who has upgraded his iphone 3G to 3.1. His phone has never been jailbroken and wants me to jailbreak it for him.

Since it is not possible to jailbreak 3.1 on windows and there have been reports of 3.1 having issues....

Is it possible to downgrade to 3.0 from 3.1 and jailbreak the phone on 3.0?