Lower your Memory Multiplier with that high of a FSB. If still at stock 3.33 multiplier, then it will be running the memory at 833mhz, which for cheap 667 rated ram, would most likely cause a lockup, or not even post.
FSB changes effect more than just the CPU itself. Increases in FSB also increase your HT link, your NB frequency and memory. When raising the FSB that much (25%) you have to lower your multipliers in the other areas to avoid instability.
Lowering your memory multiplier
HT link @ 1600
NB @ x8
But imo, your ram is most likely what is restricting your OC, and you might already have hit the ceiling with your current config.