I've got the exactly same problem on same car/age. It started to not release, and finally, even with pliers, we couldn't pull up the lock - so the door is permenantly locked.
We stripped off the door panel, but the mechanism seems to work fine - but for some reason, which cannot be seen, it is not releasing - door handles can be pulled up but it is still acting as though it is locked.
John-Mark, December 2008