Here's the original thread for reference.
here.
You still haven't said whether or not you updated your BIOS. Since the GF4 is fairly new, it's very possible you need the latest BIOS to work right with it.
Some PCI slots share IRQ's regardless of how Windows assigns them. Check your motherboard manual for IRQ assignments for each of your PCI slots and see which ones share. Just to rule out the possibility, you might try removing all of them except your video card just to see if you can run stable.
If you decide to go with a new motherboard, try something with the VIA KT266a or 333 chipset. Abit, Asus, and Epox are all good brands. Avoid the KT266a Epox board though. Some GF4 cards won't fit right due to an oversized capacitor near the AGP slot.