Did you try some voltage settings with BIOS 18? Just for fun..
A question BIOS 18 did reconigze exacly your CPU?
Little overvolt on the CPU and N.B / CPU_VTT settings could be heplfull, remmenber only change the N.B voltage if you do some active cooling on it you will need some cooler on N.B. Help me a lot here.
Very easy task by the way, just 40x40mm 4 U$ fan with 3 pin pwm connector. Some 1.43v on N.B and 1.36v could do the trick very well for FSB1333 and a QUAD CPU with stock settings, some 1.28v on the CPU could help, just for fun really... huauhauhauhauh
See ya