How new is the machine? What color are the belts you are having problems with? There have been some issues with some of the belts. I would have to look back through my notes from the dealer meeting a couple months ago to find the info. Something about the cords not being evenly spaced inside the belt causing it to roll off easier and also break easier. I believe this was only a problem for the newer ICD deck belts.
Might be something to ask your dealer to look into for you.