Maybe some of them aren't named correctly and you could be downloading the same file more than once...check this thread out it will explain how to check your files using the Bitzi web lookup..
http://www.gnutellaforums.com/showth...threadid=37676
Also maybe dont do 15 at once start them and then hit the cancel that will then send the file to your incomplete folder and you can then resume it at a later time...
Let us know if this helps....