Hello,
I recently had a similar problem with my van. It is a thread posted on 5-9-07 called "2000 venture van won't unlock...with the door buttons". For you, since the only door that won't unlock is the driver side...I would look at the hinge of the door. This is where (day after day) you open and shut it. Pull back the rubber protective cover and check out the wires. Whenever you are looking for broken or corroded wires always remove the electrical tape...otherwise you might miss it. I hope this helps you.
Mary Jo