Are you connected to the network? Do you see 4 green or blue bars in the lower left corner in limewire.
If you have a good connection, it could be your connected to some bad hosts/ultrapeers. Try the suggestions for filtering them out in this thread:
http://www.gnutellaforums.com/downlo...ms-search.html
If no joy, then post your the details of your set-up:
System details - help us to help you -> Provide these details when you post!!!