DFI + RedlineXP4000 issue: can't pass 254Mhz HTT

[Jack]

Recently i bought a DFI Ultra-D and Mushkin Redline XP4000 memory.
Today i finally had some time to play with it, but overclocking gives me problems...

I immediatly flashed my bios to the 510-2 modded by Hellfire bios.

I started out with 3,2V (with the 3,3V jumper on).
This lead me to 254MHz. 255Mhz instantly reboots.

Then I did the Bigtoe jumper trick and set Vdimm to 3,45V.
But still reboots at 254MHz.

Then i flashed to original 510-2 bios.
This didn't help anything. Still same result, no matter what voltage 255MHz reboots.

Then i flashed to 331-2 bios.
Which gave me worse results.

I tried the yellow and the orange slots, both give reboots at 255MHz.

The A64Tweaker setting i used:
1
2
played around myself with different settings
and SPD timings.
Nothing helped.

I tried multiplier 9x and 10x. Still reboots at 255MHz.

The cpu, my FX55, did 11x262,6 on my Neo2.
So i guess it aint a memcontroller issue.
My bh-5 that does 262,5MHz wont do cas 2 on the DFI
Changing from cas 2.5 to cas 2 in A64Tweaker results in a freeze.

I'm kinda out of ideas...

Can someone help me out?



Edit:
Don't know if it's relevant to tell,
but i'm running Win2k3 with only directx9.0 and nvidia chipset drivers installed.