2 XP clients, 1 2003Server, 1 router 1 XP keeps timing out on Internet

The 4 devices in question are a Linksys WRT54g Wireless router[192.168.1.1] (not used for Wi-Fi). Win2003Server for DNS and accounts and the 2 XP-SP3 clients[192.168.100 &.101] with static IPs. One station[192.168.1.100] every now and again times out trying to get on the Internet (yet can ping the server 192.162.1.103).Station 192.162.1.101 is fine. I do a tracert on both clients & get both responses to ISP. The only way to get client .100 to respond to the Net is to Reboot. HELP! Powering down modem & router does not help. Machine is clone ASUS A7E Socket 939 AMD64 3200+. Changed onboard NIC with add-on Nic & cable. No change. I re-installed the OS even. It has started timing out again (Firefox or IE). It will work if I reboot the client.