I've got an odd situation where only the number 6 PCIe slot works. None of the others do. When my TV tuner card stopped working, I moved it around to see if that would solve the problem. When it didn't, I then moved the graphics card around and discovered that it only works in #6. I admit to feeling pretty foolish about this and am hoping it's something simple that I'm overlooking.

cpu = Intel i7 Core 6 3.5 mghz
32 gb of RAM
nVidia GE Force GTX 780 graphics card
Hauppauge 2250 WinTV tuner card