Overclock problem on reboot

[Pilgrim57]

Although I was down to about 40 cpu SETI units I lost them after 3 BSOD
& SETI disappeared from project list in BOINC. Reattached to SETI but it doesn't read the wu still showing in data folder.
[Rostta OK & CPDN was suspended as lost work in past, OK]

HELP!
Q9550 @ 445 MHZ x 8.5 = 3782.5. volts 1.30625
RAM 1066MHz @ 1069 2.1v
Both CPU GTL 0/2 & 0/3 are on auto. Did try 0.675 and 0.680 but got BSOD with these volts
CPU PLL 1.52
FSB termination 1.38
NB 1.38
GTL reference0.655

O/c is 100% stable except when it comes to reboots for updates.
BSOD as desktop loads, & can get into a negative loop where uping volts has no effect so have to drop o/c back to 400 x 8.5. After running at the lower setting for some time, several hours, can return to higher settings OK
Have tried CPU volts at 1.3125 but doesn't seem to have an effect.
Bluescreen view gives errors as hal.dll and ntoskml.exe

I thought I'd try here first - so any thoughts or advise gratefully received.

 

[Pilgrim57]

It used to Biffa but I upped the volts to NB, FSB term & CPU pll & that cured it for +95% of the time.
Just v annoying that the PC runs without a hitch except when a go a restart at the higher settings. I'm out of my depth as to which I should tweak
As I said using setting for a 4.2GHz o/c as a guide & getting close to those settings @ 3.8 except for CPU volts when I'm kept lower to stop the temp increase.

 

[Pilgrim57]

Hi Biffa - the mobo is ASUS P5Q-E + Corsair 850watt modular bought in June [about 6 weeks before they brought out the new gold standard ones].

 

[Pilgrim57]

More BSOD's & with a little more tweaking seems I need a GTL reference of 0.66v & I have increased PCIE to SATA voltage by 0.1 to 1.6.
I presume this feeds the hard disks signals/data I/O? If so that would explain the hal.dll error.
Comments or words of wisdom welcomed.