It doesn't want to POST at 3GHz or above. With this mobo I have to enter the Rated FSB (or QDR) which works out to be half the clock speed on the e6400. 1499MHz seems (at the moment) to be the highest QDR that the system will post with.
I'll have a little play with the voltages. I think I've already increased the NB to 1.31 from 1.2, how high (conservatively) is safe?