Did anyone ever find a solution to this? I have replaced my battery in the fob but still have the problem and always have to scrape around the door with my key to unlock it (sometimes it will go off when I unlock with the key too). It sets the alarm off almost 100% of the time with the fob. It goes off frequently when using the interior lock/unlock buttons on the doors. I do notice that sometimes when I lock my xB, the drivers side lock does not go down (it moves but pops back up). Does that indicate my lock actuator is the problem?

 

I changed my drivers side door lock actuator with one off Ebay, and the horn and alarm stopped going off when unlocking my doors. Mine stated doing the same thing, thought it was the battery. Sat in the car one day and locked the car. Noticed the drivers side lock did not stay down.
Since I replaced the accuator 4 months ago, the horn has not gone off once.
I hope this helps. I tried looking for answers when mine started doing this, and it was hard finding anything. Finally saw someone posted about the door accuator, and it works.
Good luck.