My 4th PCIe slot doesn't work? MacPro5,1

[tuchubby]

So I have tried every PCIe device I own on my 4th PCIe slot and it doesn't seem to pick up anything, not even my original Radeon HD 5770. I understand it is PCIe 1x but no device will show up. Anyone with this experience or have any idea why this is happening?

 

[thornslack]

Slots have occasionally been zapped dead from ESD or overdrawing power, or I suppose there would be risk if the computer were plugged in or running when equipment were changed. Did it ever work or have anything installed there in the past?