im having the same trouble as you..
2.485.0 is the highest ive got it so far on stock (fixed) voltage. i have upped it from 1.450 (i think thats right) up to 1.475 (one stage up) with central brain identifier and then taken it a little over 2.5 with sucsess, but the voltage re-sets to 1.45 on reboot and it becomes very unstable.. blue screen h£ll.
there is really isnt much to adjust on my mobo and the only thing that isnt locked pretty much is the FSB. the mobo automatically adjusts everything apparently if the FSB is altered to help with a basic kinda o/c'ing..
appart from the voltage that is
been watching this thread with interest and good luck! al