socket 754 processors werent good overclockers. I had a clawhammer 3200 754, gigabyte k8nxp motherboard. If i tried to overclock fsb at all the machine refused to post. Didn't matter what settings i used. If you're going to overclock i'd suggest investing in a 939 system. The 754 are going to be discontinued anyway.
As far as useful information goes,
crank up the voltage to like 1.65 or 1.75 (im not sure what the default vcore for newcastle is)
downclock memory (as your instability could be caused from memory)
set the hypertransport to 3x (i had some issues with ht speed and ocing on my system)
Work the fsb up slowly by 5-10mhz increments. I noticed that my system would run more reliably when i did things slow.
AMD 64 x2 3800 Venice @ 2.0
Zalman 7700 @ 28c
2 x Samsung 1gb DDR400 CL2.5
2 x eVga 6800 256mb GT
430mhz Core / 1.1ghz Memory
Sandra Memory Bench:
Sandra Cpu Arithmetic:
Eat your heart out intel.