Things that sit connecting for ages & then need more sources are usually fake files. The thread below has more info & tips for these
Fake files showing up in search results

If all files that will download are going really slowly (even with multiple sources), try a file from here & see what speed you get
http://www.magnetmix.com/video.shtml

Deleting LW's preferences folder might help, see points 2 & 3 below for instructions
Fixes for LimeWire

If that magnetmix file downloads slowly too, let us know if you're seeing the firewall icon (brick wall) & also who your ISP is