iCloud Account Password
This happened to me not too long ago (not upgrading to iOS6 but for when I signed up to iCloud). The problem was, my Apple ID was using a very weak password (6 characters, all alphanumeric, no capitals)
Apple had changed their password policy to this:
When creating an Apple ID to use with iCloud, your password must have a minimum of 8 characters, a number, an uppercase letter, and a lowercase letter.
To get access to my account I needed to change the password to something that followed these guidelines, and of course now I use a super secure password.
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