Check your ultrapeer connections. Get rid of all the Gnucleus vendors and don't leave too many Morpheus: try for as many Limewire ultrapeers as possible. You can also max out the number of ultrapeer connections, which varies according to your internet connection (in prefs.). Then you can check to see if too many ultrapeers are from one ISP. I have also seen the same vendor ("real" IP) with different ports.

Do repeat searches for active downloads, and until hashing is a feature, try to find a file with the most common name so you have a better chance of resuming the dl should it be interrupted.

The other factor is that people do not share, or they share files of value.