Missing memory when X540 PCIe present

[nry]

I have some Intel X540 dual 10GbE network cards which I put into the below setups.

But for some reason setup 1, boots fine with no errors but only registers 24GB ram even though there is 32GB installed, remove the X540 and shows 32GB ram.
I have tried different PCIe slots too...

Setup 2 will not post with the X540 installed unless I remove one of the memory modules. When it dosen't post it shows error code 55 on the Asus diagnostic LED display

Setup 1:
Asus P8B-WS
Xeon E3 1245
4x Corsair Vengeance 1600Mhz DDR3 8GB

Setup 2:
Another setup
Asus P8B-WS
Xeon E3 1245
4x Corsair Vengeance 1600Mhz DDR 4GB

Anyone got any idea what would cause this? And how it can be solved?

I have run memtest, all ok. Installed the cards in other machines without an issue

 

[sleeprae]

I had a similar issue on an eVGA X58 board with a Dell PERC6 installed. One of the memory channels would fail to detect. Taping over the PCIe SMBus pins (B5 and B6) resolved it.

This thread has an image, though the OP's complaint is about the card failing to detect:

http://communities.intel.com/thread/24587

 

[nry]

Thats the first time I have ever seen anything like that!

But will give it a go, thanks

 

[nry]

Cant believe this worked, still got to try the other machine

Thanks!!