If you're wondering WhyAmIgettingPciErrors, verify that you are following any PCI population rules required by your system.
For example the Intel SR2400 comprised of an Intel Server Board SE7520JR2 combined with the Passive Full Height PCI-X Riser Card required add-on cards to be populated starting with the furthest slots from the mainboard connector. When cards such as NICs are inserted in the middle or lower slots, newer BIOS versions halt during POST and inform the user about the population rules. Older BIOS versions would not catch this and users would intermittently experience PCI errors. With certain BIOS settings and OS versions, these would appear as NMIs.
Any large passive riser should be suspect if you are getting PCI errors. It is possible that signal reflections are occurring. If no population rules are available for your hardware, just assume you should move cards to the end of the PCI riser furthest away from the mainboard. This both dampens any reflections, and avoids placing cards where reflections would tend to cancel out the signals.