Internet disconnects after 12 hours

[carygeezer]

Good day. I am running a Tyan Trinity i875P (S51501ANN) motherboard with an Intel P4 Northwood at 3.2 GHz. The OS is Windows XP Home Version 2002 with Service Pack 2. The BIOS is Phoenix Award Tyan version 1.12. Everything works great except that about every 12 hours the TCP/IP stack appears to freeze. I am wire connected to a Netgear Router (MR814 V3) at 100 Mbps which is then connected to a cable modem. When the freeze occurs Internet Explorer will open but will not connect even to the router. This worked the same with a Linksys router so it's unlikely that the router is the problem. The connection can be restored by booting the router at which point it will last for about another 12 hours. Booting the computer does not fix the connection. The computer is using a fixed private IP address in attempt to eliminate DHCP as a source of the problem. I have been trying for 6 months to fix this problem. Tried a better power supply, a new PCI NIC, a UPS for the router and the computer, disabled GBe LAN, turned off IPSec. None of these moves have solved the problem.

I'm looking for new ideas of things to try to solve the problem since it is an annoyance since you never know when it will quit working. Any help would be greatly appreciated. Have you ever heard of a problem like this?
Thanks in advance for your help. Larry

[AzureIce]

Try hooking the computer directly into the modem and see if the problem still occures.

[carygeezer]

Good idea. I'll have to wait for my wife to be gone for a while since she uses the connection a lot. I'll let y'all know how that turns out. Larry