I downloaded the iPhone 4 IOS 5.1 upgrade after being nagged to do it by my phone - now the Internet won't work and I keep getting a message that I'm 'not subscribed to a cellular data network' - which I am, of course.
I'm on Vodafone PAYG and I'm in credit. Had a similar issue with the last upgrade and after a quick Google I changed some network settings, which seemed to resolve it.
Now the same fix doesn't seem to work. I'm tearing my hair out here (lurking on free cafe wifi).
Can anyone help, PLEASE?!!