Try this:
1) create a new gmail account on your computer.
2) call your cell phone with a different phone.
3) answer your cell phone then hit the back button and it will take you to the home screen.
4) turn on wifi so it can do data and voice at the same time (remember that the phone is still connected)
5) go to Settings -> Location & Security and disable lock pattern (you'll need to enter to correct pattern previously set)
6) go to Settings -> Accounts & Sync and click "Add Account" and add your newly created Gmail account.
7) hang up the phone.
8) turn the phone back on, at the lockout screen, enter your new Gmail account info and it should let you back in
9) once the phone is unlocked, you can go in setting and remove the newly added Gmail account and keep the old one.
(And sometimes you have to disconnect your wifi connection and then reconnect and before it will work.)