I've read about it on the forum before. The virus replicates itself in a folder called complete and the number of files your sharing balloons to hundreds or thousands and those files are shared which keeps the virus spreading through the network.
Are the files all the same size and all the same type but with different names?
It sounds like a virus. Here's some examples of similar posts:
http://www.gnutellaforums.com/showth...threadid=41194 http://www.gnutellaforums.com/showth...threadid=40380 http://www.gnutellaforums.com/showth...threadid=40738
Hope this helped