Not 100% sure but if you can't lock your AGP bus (which on that board I don't think that options exist, but that's what I'm not 100% sure on) then I'm surprised you even got your FSB that high.
AGP bus has to be locked at 66MHz which automatically locks the PCI at 33MHz.....without that it's going to follow the FSB up and stop pretty short.
Also if you've read that guide at the top you'd already know those answers pretty much