thanks. i reset all the bios settings to standard, then turned the dram voltage down to 1.5v (from 1.6v ?), set the dram frequency to 1600MHz and it's all running fast, stable and cool.
i've also turned up just the cpu ratio on the overclocking utility from 18x to 24x and it's still stable and cool.
processor now shows as running at 4.8GHz up from 3.6GHz!!
all temps are low to mid 30's, upping to low 40's when working hard.
thanks for the advice nikorr.