I had a similar issue with mine. When it first started, it was just as you described, but it progressed. The fob stopped working on EVERYTHING (alarm and trunk included), so I just chalked that up to the connections on the fob being crappy. Never replaced it, just manually locked my doors (literally pushed the sticks down one by one), and manually unlocked them with the key. Then one day, my door locks started locking and unlocking as I drove down the road. My hubby replaced the drivers side lock switch ($20 or less thru GM), and no problems since. (Granted she's been parked for 2 months ish now, but still, I drove her for about a year after he replaced it, and she was always fine.) If you start getting "possessed" door locks, I can about guarantee that it's just that switch. The hubs did mine along with 2 others around the same time, and none of us have had problems since (the other 2 are friends of mine who still drive their balts). Honestly, if you can figure out how to change that switch, I'd throw the $20 into the car and see if it fixes it. I don't have a clue for sure, but I wouldn't be surprised if the messed up switch may have led to the messed up fob in my case....