Hi there,
I believe I am having a similar issue to the original poster. The card (same as OP) won't allow the MB to post if the TBS card is in the PCIe X4 slot, but it works in the PCIe X8/16 slot. The problem is that this slot is very close to the graphics card, obscuring part of the fan, and I'm worried about overheating.
Can you please confirm that the issue is the same, and is there anyway to fix this? The MB is a Asus ROG Maximus IV Gene-Z Z68 chipset.
Please let me know if you have any questions.
Many thanks in advance.