If you are having issues updating to iOS 5.1, and getting error messages in iTunes about your device not being eligible, there is a quick fix at http://www.iphonejailbreak.me/fix-this-device-isnt-eligible-for-the-requested-build-in-itunes-during-ios-5-0-1-update/ .
I haven’t modified my phone in any way and Apple’s support page is no help (as usual).

If you are having issues updating to iOS 5.1, and getting error messages in iTunes about your device not being eligible, there is a quick fix at http://www.iphonejailbreak.me/fix-this-device-isnt-eligible-for-the-requested-build-in-itunes-during-ios-5-0-1-update/ .

I haven’t modified my phone in any way and Apple’s support page is no help (as usual).