Internet access probs

I have a broadband connection (XP Pro, Dynalink RTA100+). Everything was working fine until I installed SP2 two weeks ago. Now, 9 times out of 10 when I reboot I cannot reconnect. More than that, sometimes the XP firewall turns itself off and I have to reboot again. The only sure way to reestablish my connection is turn the router off, reboot the computer completely and turn the router back on. The symptoms are the same whether I use a USB or LAN connection. Even turning the XP firewall off permanently doesn't work. Anyone know whats going on?