Had this problem on my iPad 3/Wifi/3G. I went through the Apple phone support route, painful as it was with getting satisfactory proof of purchase etc. and jumping through all their hoops. But eventually after a few days, the iPad was unlocked and I was able to activate it, more or less.
There is still an issue with iCloud but only on this device (2 x iPhones are OK). In "Settings" - "iCloud" it says "account not verified. Check your email at .......for instructions etc etc". Problem is that the email address listed is corrupted, as in "gmail.com" has become "gmal.com". Obviously there is no such email address and it is not possible that my device has ever been registered to that address because it does not and never has existed.
That explains why it wouldn't accept my activation details after the 9.3 update, it wanted a "gmal.com" in the userid. So it appears that 9.3 has caused the corruption. I can now use the iPad for most purposes, but not for any iCloud related use. My next step is to head to my local Apple Store to see their reaction. I don't really expect them to be able to resolve it, but something may filter back to "Head Office" to prevent future recurrences.
