I had almost the same problem, except it was ALL the back lights. It turned out to be (after several hours of checking wiring harnesses) a shorted wire in the back hatch, by the handle/latch. Apparently, a wire had gotten pinched, and finally rubbed through, causing a short. The tip-off was the brake light fuse kept popping as soon as it was plugged in.
Good luck. As code58 said, check the fuses, then just go on down each line until you find the problem.