Can you download music files without a problem? How's your connection (fair, good, excellent etc)? Do you see the firewall icon (brick wall in front of the blue earth)? Who's your ISP?

Delete your preferences folder (ooh I just love saying that) with LW closed
Fixes for LimeWire

(just make a note of any settings you're not sure of within tools> options. You'll need to reset everything afterwards)