DavidF.C280 (I keep thinking that that's me when I see that!!),

It seems as though you have already figured your problem out, but just so you know, you can find out how many current, and stored poly-V-belt recognitions there are via your Climate Control Unit.

Press and hold REST (car and climate control on) for about 5 seconds until you get the number 1 and another number (in-car temp), it should flash between the 2 numbers. Press the ARROW down, to direct the air to your feet, that should put you at menu number 52, which is the number of stored slips in your poly-v-belt. If you press the button again (air flow to feet) you should be at 51, and that tells the current number of slip recognitions in the poly-v-belt.
Give it a try! Good luck!

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)