Lets think about the connections, does mozilla work? (you are not using IE like a smart user right?)
If you are running a firewall like zone alarm, make sure it lets this program make OUTGOING connections at the minimum, and you should let it be a "server" meaning incoming connections to port 6346 (if thats the port you have set.
Now, if you are at a university you may be screwed because your admin sucks and he has blocked gnutella packets.
No problem, being screwed just gets you mad and then you find out that a group inside your network shares internally on a private LAN, just watch some packets on your network or ask around.
Point being, if your browser works, Gnuc should too, but if not then something is wrong out on your network, or maybe, just maybe you have that "newdotnet" or "savenow" spyware thing that tries to redirect connections (this is a long shot), search on google for solutions to get rid of them (via uninstall mostly).
ok, enough, this is basic, now tell me more if it still has problems, or tell how you got it working for the next guy.