If your processor is an 800fsb model then your Fsb should be 200Mhz, this is quad pumped to 800fsb.
And it's not only EE's that have the 800fsb.
The other thing to check is that your memory is running at a ratio of 1:1 for the highest speed. (as long as it's at least PC3200). That's 400Mhz x 2 to give you 800Mhz. Confusing isn't it.