Replaced door lock actuator, can't open door

[Multibeemer]

The front passenger power door lock on my '03 4.4i stopped working recently, so I bought a used one from eBay. I tested it outside the car first to confirm that it works, but after installing it in the door, I have two strange problems:
1) The actuator, which worked just fine outside the door, now doesn't work, either when I press the button on the key, or the one on the center console, and, more pressingly,
2) I can't get the door open! When I pull on the cable, I can feel the latch moving, but the door won't budge. Manually pulling up on the door lock button's lever doesn't help.

I've replaced several door lock actuators on my various BMW's over the year, and I've never had anything like this happen, so I'm thinking that, as usual, there's some obvious detail I've overlooked. Any idea how I can get door open so I can start troubleshooting why the actuator stops working when it's in its home inside the door? Could the two issues be connected? I have a feeling I have a major dope slap coming on when somebody points out the bone-headed thing I'm either doing or not doing. Thanks.