I just wanted to put this out there in case anyone else has the same problem. I had set up an Android 2.3 phone with 2-step verification (2-factor authentication). Somehow, I pocket dialed and it went through my limit for unlock pattern attempts. When I pulled the phone out of my pocket, it was prompting me to sign in. No matter what password I used, it wouldn’t unlock. I even tried the backup verification codes I’d printed out a while back. I finally went to my Google account on the web and generated a new application-specific password for the phone and it let me in. I revoked the old application-specific password.