Since all your other lights work - could still be a fuse problem, would check all of them (someone posted in the Armada forums that they had the same problem and he tought all his fuses were fine until he looked individually at each one and found one burned out.)
You should also take a good luck at your connectors, I had one rear turn signal go out and the bulb was fine, fuses were fine - then I looked at the connector and one of the wires has corroded so badly that it couldn't make a connection anymore to the bulb wires. I peeled back the rubber boot of the connector and soldered a new wire in place - Bob's yer uncle/good as new!
Could also be an issue with the connectors/electrical relays, see image below (could be body sub harnesses 151 or 104):
I'd get a voltmeter and check to see if you have continuity at those pins.
Good luck - let us know how it all pans out.