Does this happen with every file? How well are you connected? Have you used LW before without a problem or have you just downloaded it? Don't make me guess
Do this port test & see what result you get http://www3.limewire.com:6346
Do you see the firewall icon (brick wall in front of the blue earth)?

It might be the vendor
http://www.gnutellaforums.com/showth...wnload+0KB%2Fs

or try the fixes here
http://www.gnutellaforums.com/showth...download+speed

or it could be your ISP. Try downloading a magnet link as shown here & see what speed you get
http://www.gnutellaforums.com/showth...download+speed

While there's nothing to say that Comcast do block p2p, a few people have had probs
http://www.gnutellaforums.com/showth...hlight=Comcast