something to look at is your FSB,are you overclocking?
the agp/pci dividers,if not available in BIOS,
are usually set.maybe a corrupt bios?.
A FSB@133 shouldn't cause problems.Have you tried
lowering the FSB to see if the same thing happens?

on Win 98se,can this registry value for SingleChipAASLI
be changed to enhance a Voodoo 5? mine reads:
tweakvalue "SSTh3_SLI_AA_Configuration"
Voodoo5
A'merlin2.9
glide2x,glide3x
athlonxp1700+
win98se
DX9

there is a reg.tweak for at least i know Win2K,when
using Athlon CPU,a known issue is right,WINGUIDES.com
has this tweak.maybe works or gives idea
to fix more problems too?