iPhone 3g wifi issues

Ok, so I started having wifi issues with my iPhone right about the time I upgraded to the 3.0 firmware. Basically, I may be able to get it to connect to a wireless access point or wireless router, but after 10-20 seconds, it will drop the connection.

I've tried reverting the firmware to the 2.2.1 version, but it would never complete the process. I tried reverting to 2.2.0 and got it to work, but wifi still didn't work. I put it back to 3.0, and now it won't even connect to my wifi at the house.

Has anyone else had this issue? Am I destined to take it to the Apple store and see if they will replace it? Any tips to get it to work without dealing with Apple?

BTW, I have only jailbroken my phone once, but decide to take it back to a non-jailbroken state for some reason. It has been quite some time since I've done this.