i am using an officially unlocked iPhone 3G and I am facing the same wifi problem . It was working a couple of days back but suddenly it stopped working . I updated to 3.0 a week back and since then I'm facing n no. of problems . I've restored my phone a couple of times after that and still no help ; Now even I'm planning to go back to 2.2 . Do tell me if it worked for you when you went back to 2.2 .