Try downloading the newest version for starters.

Secondly, wait a little while for all your connecetions to the gnutella network to be established, like say, five minutes.

Thirdly, if that doesn't work, make sure you share files so you're not considered a freeloader.

But most importantly, have you changed your internet settings since this problem started, and are you behind a firewall (hardware or software) or a router that has a firewall?