I had the driver's side door apart to install the SBC lift, but since the passenger side window isn't broken yet, I decided to wait for the inevitable failure before I went to the trouble of the install. When Tom helped me out with the step bar install a few weeks ago, we sprayed white lithium grease down the door to lube the tracks but didn't take the door apart to do it.
It's a good point that maybe the driver's side lock was fouled. If both door locks run through the same circuit loop, it's certainly possible that a loose connector in the driver's side door could disable both doors. Thanks LDub.