iTunes Password prompt after iPad update to iOS5

I just updated my iPad 2 with the iOS 5 last night. Today when I woke up, a prompt box popped up in iTunes asking me to enter a password to access my backup files. But I never set a password.It must be an iTunes bug and the key is that it is a password used on your device. I tried using my Windows user account password on my PC and solved my problem. Your Facebook, Gmail and Twitter on your