iMessage suddenly quit working on my iPad 2 and iPhone 3GS, yesterday. I am traveling and was very frustrated with the fact that I was not able to iMessage from overseas. As it turns out, I tried everything. I updated my iPhone to OS5.0.1, but left the iPad at 5.0 (just in case). I tried reboot, repowering and even reset my apple id and password. All that did not work.
As I was forced to change my password to meet the new 8 character, capital, number format - this caused panic in accessing emails, mobile me and other things. Resolved those issues, but iMessage still would not verify or activate. I tried resetting Facetime settings, iMessage settings and numerous other settings.
Alas, the solution was to turn off location and set my time zone to automatic. I have had to adjust the timezone manually as I am traveling and do not have satellite access all the time.
This works, finally my iMessage and Facetime were activated.
Hope this helps someone else. Suggest making sure your time zone is correct before trying to verify or activate before changing a bunch of settings and passwords.