This is the second time this has happened on my 2000 Civic sedan, and both times it has been after I've manually pushed the lock down. It won't unlock with the switch, with the remote unlock, or even with the key. When I try the switch or the remote, it looks like it's straining about halfway up, then goes back down. If I try to unlock it with the key, the lock again only gets partway up and I'd break the key if I tried to turn it with more force.
Last time it happened, I tried the remote one more time as I was walking around to get in the passenger side, and it suddenly worked out of the blue. This time I was already inside the car, and it basically wouldn't let me out. A bit of a safety issue, wouldn't you say?

Update: I tried again about a half hour later. Still wouldn't work with the remote. I kept fiddling around with the key and finally, with a little effort, got it to pop open. After that it would open and close just fine. Something sticking in my lock assembly maybe?

 

Your problem could be caused by a number of things. Has there been any recent exterior damage to the door, such as any hard impacts? Did this abruptly start happening, or have you noticed anything strange in the past that may have been getting progressively worse?

 

Did you recently remove the door panel? because it happened to me too, i took the door panel off and after i installed it again and tried to unlock the doors, it would unlock halfway and then go back down. Turns out something was in the way and it would automatically take it back down.

 

I haven't removed the door panel, and I'm not aware of any recent exterior damage. The only common thread I can think of is that it happens when I push the lock down by hand. It started abruptly, but it's only happened maybe 3 times in the last 10 months or so. As such, it's not causing me any major issues.
That being said, if you see a headline that reads, "Man remains in Civic while car burns", that's Murphy's Law biting me in the butt.

 

It just happened again last night. This time, I hadn't manually pushed the lock down, I just locked it with the remote. No amount of fiddling with the key would get it unlocked. It's getting very frustrating. I think it's a safety issue, but I don't know if that's enough to get me off the hook for an expensive job at the garage.

 

Have you tried taking the door panel off and tried unlocking/locking it? It may be getting caught on something like said before...Or the metal rod that drives the lock could be bent from manually locking it. I'd try taking the panel off if you're comfortable working on that stuff and start from there. It also might be the locking motor! If it's not the rod, I'd be checkin' out the motor making sure that it is working properly. The easiest way I can think to do that is detatch the metal rod from the lock button itself, and actuate the power lock. If the rod doesn't move very far at all, then I'd say the motors shot.

 

I'm not sure whether motor or rod is more likely. The fact that it's gone from non-functional to functional a few times is really odd. I pretty much never manually lock it, and the fact that it works sometimes seems to suggest that the rod isn't bent. Of course, I could say the same thing about the motor, since last time it happened, I got it working and could lock/unlock it remotely over and over with no problems. You'd think it MUST be getting caught on something, since turning the key isn't working...
I'm not really comfortable taking the door panel off (never done it), so I don't know if I'll take a shot at it or not. I'm just worried that it'll cost me a bundle just to have it looked at.

 

I just called the garage and they right away, from the description, told me it was a door actuator problem. $80 + parts, and the part goes for $145. So I'm looking at around $256 after taxes to fix it if they're right. Don't see that I have much choice - I can't very well keep going in/out the passenger door.

 

You could save a little bit of money by going to get the part yourself, and just letting them install it.

 

I would just take the door panel off myself. I have done it several times and it is very simple. All you need is a phillips screw driver.

Good luck! If you mess anything up, at least you can pay for it to get fixed and it will cost you the same. If you fix it yourself, you just saved yourself a little over $200.