I had this same issue with the 2001 I just got. I managed to get the back hatch open, took off the plastic panel so I could get to the back side of the locking assembly. There is a plastic retainer clip on a threaded rod. I used a small screw driver to get the plastic retainer open, moved it down (away from the end of the rod) and clamped it back on. Now the back hatch opens and my power locks all started working.
If you cant get the rear hatch open, you might be able to get the plastic panel off from inside while it is closed.