After restore, iTunes wants a password?

[trinigianetti]

A friend of mine asked me to try and get his wifi working on a old 2g iPhone. He is running 3.1.2
I tried the network reset trick. That didn't work, so I decided to restore.

We backed up the iPhone to iTunes. Normally the phone has a finder passcode lock for everyday use.

I then did a restore. When we reconnected to iTunes to reinstalled the back-up from the last sync, iTunes is asking for a password.
I've never entered a password when syncing before. I thought maybe it was referring to the phone passcode. But that did not work. I tried the computer admin password, that did not work.

Any suggestions? The info from that last back up is crucial as it has notes we need.

[CaptainChaos]

Did you password encrypt the backup itself? Maybe that is the password it is looking for.