Your ISP has almost certainly started to block not only Gnutella but BitTorrent as well (BitComet is a BitTorrent application and does not connect to Gnutella)

Have you been doing some heavy downloading this month ? If so then you might have used up your quota for the month

You should try and talk to your ISP about the problem

They could be only portblocking. Are you using the default port for Limewire and Bitcomet (unfortunatly can't remember myself what BitComets is. Limewire is 6346)