I've run into the same problem. Remember that you're running the cpu way out of spec That being said, sooner or later you're going to hit the limit, whether it's the FSB, multiplier or a combination of both. You've probably hit the limit on the multiplier at that FSB. You are running a cpu intended to use a 100MHz FSB at 155, hitting 950, not too bad.
I'd try backing the FSB down a bit and increasing the multiplier, that may help, I did that with my DURON 600 on an ASUS A7V133, it would post and run at 9*122, but runs much better, (and cooler) at 10*111, higher scores in SANDRA etc. Try that, then see which performs better in the tests.