Door locks seized on 2000 Cavalier?

Have a 2000 Cavalier and the door locks appear to have seized, unable to unlock via the latch inside, remote, or key. They always felt a little stiff, but didn't think anything of it. Thought it might be the security system, so I disconnected the batter but nothing changed. Remote appears to be working fine. Can't even get the door open to remove panel or access fuse box. Does anyone have any ideas? Thanks!