Stable At 146.7fsb Not At 150fsb

I have a ECS K7S5A mobo, so the only way for me to o/c is to increase the fsb.
I d/l o/c bios and set fsb at 138/138. Increased to 146.7fsb thru CPUFSB. my systems very stable. but when I increase to 150fsb my system locks up. have to unplug power cord to reboot.
I have not unlocked my cpu and have not o/c my vid card or memory.
Is there anything else I can do to get my system stable at 150fsb?

maybe changing your memory timing or trying taking out all your pci cards to see if you can get higher