Yep, it's a known issue. Take it to the dealer. There was a series of clocks that did this. Had mine changed a few years ago now.
I believe it was a TSB. I'll check my paperwork in the car. I just saw it the other day, so hopefully I didn't chuck it already.
Heh. In my case, the clock was replaced, and hasn't gained/lost time since. Maybe to the detriment of arriving at meetings on time. I finally dug my paperwork out. I took delivery on 27 Sept 05, and the clock was replaced on 20 Jan 06. It was replaced at no charge, but I can't tell if it was a TSB or warranty issue. I seem to remember it being a TSB, something with a series of the clocks that were manufactured during a specific period, affecting mostly early 05 builds. It was a little surprising that mine was also affected, but maybe they were digging in the bottom of the parts bin that day.