Spargo - my 'home network crashed' thread was a a similar problem, also with a Belkin router at the centre of my network. My computers are setup differently (Win XP all round) but what has worked for me is uninstalling and reinstalling the firewall program(s) AND manually configuring the TCP/IP settings for each machine,
ensuring that they all have the same IP tagline (eg 192.168.1.x, where x is a unique number for each machine and 192.168.1.1 is the IP address for the router)
the subnet mask is the same for all machines (eg 255.255.255.0)
DNS setting is the same as that in the Belkin setup window on the 'Home' screen'
Everything works, although wireless connection for Desktop PC does not connect - the wired connection is faultless (and faster :-))
Hopefully this is helpful