internet disconnect requires reboot after idle time

Motorola Cable Modem connected to Linksys Router WRT54GX wired (NOT
wireless) to two PC's running XP-SP2. One PC has Linksys Ethernet PCI
card. Other PC has built in port on ASUS A8N-E nvidia nforce4 ultra
motherboard. Firmware and drivers all up to date. Powersaving turned
off except for monitors. After an extended amount of idle time (not
sure how short, but two hours brings on symptoms) computers no longer
see internet. Repairing link doesn't work. ipconfig /release ipconfig
/renew doesn't work. Rebooting does work, but I'd hate to have to
reboot everytime I want to check email after a few hours away from the
machine.
When I had just one computer connected to the cable modem it was always
on as advertised with no problems. Introducing the router started
problem. I've tried setting autodisconnect in registry to ffffff and
not allowed windows to power down internet card without success. After
the disconnect the two machines can see each other but neither can see
the internet. Some interaction between my ISP (Roadrunner), their cable
modem, and my router causes the disconnect (?). Rebooting the computer
(leaving the router alone) reestablishes the connection. Firewall
issues ? CA EZFirewall on computers and Hardware Firewall on Router.
How do I convince router and cable modem/ISP to stay connected?

Any ideas? Thanks in advance.

May have fixed my own problem by adding the DNS IP to the Trusted list
in my firewall. See this thread:

http://groups.google.com/group/micro...xp.general/bro...