Just the TOLUD but if you've done that already and the other cards are showing up it's a bit of a mystery.. I would be thinking it's a bad riser as well.. do you have one card on the MOBO itself? If not could you put one in to the board and then use the spare riser to test? Or just swap the riser with another?
With how the mobo is screwed onto this frame I have its not possible to mount a card directly into the PCI slot, darn it