It could very well be that MSI does not yet have a BIOS capable of handling the half-multipliers found on the Q9300, Q9550, and E8500 chips. If they don't, I am sure they are working on one, as the P7N Diamond is indeed advertised as 45nm ready.

You should e-mail MSI tech support about this issue, and you may want to start a thread on the MSI forums as well. The issues with EIST may also be a factor of missing / incomplete BIOS support.

In the mean time, I would suggest leaving everything at "Optimized Defaults." When MSI releases an update that addresses the half multiplier issue, you should then revisit your OC efforts.