In the year that I've owned my 2006 CLK 500 (27,xxx miles), the stereo and nav systems have three or four times gone down for a day or so without warning. The power switch will turns them on, but none of the controls are operational. The last time this happened was about a week ago. It lasted about a day.

A couple of times the convenience settings that scoot the seat back and move the steering column up and down on power up/down of the car will suddenly stop working and need to have the settings re-entered in the computer.

Yesterday the steering column moved to the top of its range and stopped moving up and down, but it still telescopes. The convenience settings don't seemed to have failed because the seat still moves fore and aft and the steering column doesn't move even if I move the stalk manually.

I can hear the faint hum of a motor or servo when I move the stalk, but nothing else happens.

I talked to the service writer at the dealership today and he told me that he'd never heard of this combination of symptoms and that he suspected a bad gear in the steering column and told me that it would take at least $200 in labor cost to conduct an adequate diagnosis of the problem.

The combination of the aforementioned failures - which seem like they're likely software-related - all seems a bit too coincidental for me to believe that a purely mechanical (and apparently unprecedented) failure is the culprit.

Anybody got any experience, hunches or suggestions that might be of help here?

Thanks