The System encountered a non-maskable interrupt

[Taco Fleur]

Every now and then I get the blue screen of death with the following entry in the log "The System encountered a non-maskable interrupt prior to this boot the NMI source was PCI slot 0"
I believe the array controller is in the PCI slot 0.
The funny thing is, it only happens when I enable all network adapters, there is one onboard which I believe does not cause a problem, there is one in the PCI slot, which I have moved from several slots up and down.

The machine is a Proliant 1850R, BIOS is up todate. Anyone any ideas? If the idea comes with a link please provide link as the HP site is not one of the most user-friendliest sites to find things on.

TIA