Check your disk for errors as described below
http://www.gnutellaforums.com/showth...t=disk+problem

How much free HDD space do you have? Try defragmenting your HDD.
Otherwise, check the threads below for more info
http://www.gnutellaforums.com/showth...disk+pr oblem
http://www.gnutellaforums.com/showth...t=disk+problem
http://www.gnutellaforums.com/showth...t=disk+problem
http://www.gnutellaforums.com/showth...t=disk+problem