Check the post below for a few links about disk problem (ignore the last link)
http://www.gnutellaforums.com/showpo...57&postcount=2

First of all, check how much HDD space you have left. How long since you've defragmented your HDD? That's something you could try, it's fixed the problem for a few people.
Otherwise, use the forum search to look for disk poblem & you'll be able to look through old threads.