Problem with cd multichanger / comand system

[majcam]

I have a 2001 E class (210 model), which I bought used a week
or so ago.
Great car, but I have a niggling problem with the COMAND Audio system.
The COMAND system is fully loaded and has: -
SATNAV, CD Multichanger, TV Tuner, Cell Phone, and Linguaphone
voice recognition.

Every now and again the CD stops working properly. Instead of the CD
music I just get a hissing or 'white noise' out of the speakers.
Everything else works OK, and sound works OK (i.e. TV, radio etc..)

Also I can still operate the CD , change discs, change tracks etc..
Just get hissing instead of music.
If I switch it off, and leave it a while, then retry eventually all is back to normal.

Any Ideas very, very greatfully received.

You are doing a great job here chaps, thanks !!

Mark C