There are fake / dud UltraPeers out there. If it is due to that, then close LW & reopen. Go to your Connections window & make sure you are not connected to the same U.P.'s. If yes, repeat process every 10 mins or so.
However, there is a chance it might be comcast. Somebody told me just yesterday their gnutella programs are now not getting anything & they also go thru Comcast. That person uses Shareaza.
Do you see a brick wall in front of he blue world icon at bottom of LW's interface? When you open LW, let it settle for 10 mins or so before searching. (My LW is working flawlessly.)
You could try downloading a magnet link to see if yo ucan actually download a file:
http://www.magnetmix.com/video.shtml