I have a problem. For some reason a ad keeps showing up on the top of my iPhone 4 iOS 4.1. When I respring it goes away but come back after a while. I tried to install adblacker but no luck. I also tried ip firewall but also no luck. The only thing I can think of is either format or upgrade. I was wondering if I format can I install iOS 4.1 which I am already on instead of formatting to iOS 4.2.1.