I'm not sure whether I should post this in the Graphics Forum or the Motherboard Forum, since I don't know which one is the problem.
I building a new system with an Asus P6T Deluxe V2 motherboard, Intel i7 920 CPU, and a MSI N285GTX-T2D1G-OC GPU.
I am installing WinXP SP2 on the system. I am using the default (Auto) BIOS settings.
As I was building the system, I used an old 7600 GT GPU (taking baby steps) before I installed the 285GTX.
Everything worked just fine with the system, until I installed the 285GTX. After the 285GTX was installed (but using the exact same nVidia driver set that was used for the 7600 GT), all network accesses became insanely slow - making the system effectively useless. The network worked just fine when the 7600 GT was installed.
Reinstalling the 7600 GT & reinstalling the graphics/network drivers fixed the network problems.
Another chunk of information: Only one of my network ports has this problem.
The Marvell Yukon 88E8056 Adapter #1 works fine with the 285GTX installed, but the Marvell Yukon 88E8056 Adapter #2 has the congestions problem. It seems like the Adapter #2 is having some sort of IRQ conflict or something.
Actually, I did do that (since I think that is the best way to install drivers), and still saw the problem.
This is cornfuzing - The port works fine prior to installing the 285GTX, so I know it almost certainly isn't a hardware problem with the P6T motherboard. This has to be a software or configuration problem of some sort ...