I have a 2008 S6 with adaptive cruise control, a feature I love. However, twice in less than a year it has stopped working.

The first time was after a gentle tap of the lower front lip on a curb that was a bit too high. My error -- $750 to fix.

Last week while driving at freeway speed a piece of cardboard flew across the road and hit squarely on the front of the car. Worried that the adaptive cruise was again out, I followed some cars and -- thankfully -- it worked fine.

However, today it stopped working. Trying to turn on the cruise, the car displayed "Adaptive cruise not available!" and that was that.

Has anyone else had similar experiences?