530J + P5P800 suddenly unstable @ 4GHz

[Hype]

I've got a P4 530J and an Asus P5P800, and the CPU has been running 4GHz (267 x 15) almost for 1 month completely stable!
Then the other day after I updated the bios to 1007.004 it became inzanely unstable... Now it won't even do 3.75GHz stable! :mad:
I've tried to downgrade to the original bios (1005), but without results!

I have an idea that it could be my ram (Corsair TwinX 3200XLPT TCCD - Brainpower PCB), because in SuperPI I get the message: "Not exact in round" and I get some program errors in the startup!

The cpu temp is fine... 36c idle and 48c load, and it doesn't help giving it more vcore!

I'm getting sick of this mess, so it would be great if anybody could help me! :)

EDIT: BTW, I have tried with the ram @ 1:1 and 5:4 without results!

[sin0822]

Its not brainpower, because corair dosent use it now, they use their own custom PCB, but aside from that your problem is your board i believe, do you have another lga board?

[Hype]

I don't have another 775 board to test with...
But isn't it strange that it USED to be fine at 4GHz, and now it won't do SH*T!?

[Falkentyne]

Did it IMMEDIATELY become unstable right after you flashed the BIOS, when you attempted to overclock it for the first time? It's rather important to know that.

And also,
Did you clear the CMOS when you flashed back?
You should always clear the CMOS after flashing, before powering back on.

If it was a BIOS issue, then clearing CMOS after going back to your original bios, will always put you back where you started.

I suspect a RAM/accelerator timing in the new BIOS got tweaked or perhaps you changed something that got set back later..