What happens if you disable the L2 (motherboard / external) cache in the BIOS?

What updates, if any have you installed in Windows? If you are using the unofficial service pack, that could be your problem.

Try the updates from the 2004 update CD available on vogonsdrivers.

I don't use any updates except for NUSB 3.6, but the last time I reinstalled Windows I checked that the issue was present even before I installed NUSB.

Thank you, I will try installing the 2004 updates and see what happens.

I know it's been a while, but I have given up on this motherboard. I've tried everything to no avail.

Gigabyte GA-5AX (ALi Aladdin V) doesn't have this issue in Windows 98.