It depends on if there is a divider for the pci/agp that is built into the
chipset, so that when the fsb is set to 166mhz, the pci/agp has been set
back down to 33/66 mhz. This happens around 133mhz - it depends if your
bios does the same around 166mhz. If not the pci/agp will be running too
fast - 75-85mhz and that will cause the problem as the two are tied
together. I suspect that as there is not a 166mhz fsb cpu listed, that
your board does not have this divider and is based upon the revision 1
KT333 chipset. The revision 2 has this extra divider.

Now, someone else mentioned this divider in a previous post of mine. I had
forgotten about that. I believe this motherboard (SL75-DRV5) does not have
the divider at 166, so I guess 133MHz processor for me.