yeah thats a common problem. I'm not sure if it affects peformance, but i know its annoying as hell. Mine is getting worse, now it doesn't go away. if you do a search you'll probably find a million posts about this. so far some think its just the belt, or the bearing. I'm not really sure what it is. I'd fix this but i don't think there is a write up on how to do it, so i'll probably just have to wing it.