I've got a ASUS ROG Maximus V Extreme and I'm trying to connect my fans to the chassis fan pins to get them running according to the motherboard. I know for sure that my fans work, as when I test them with my Molex connector, they all happily power on.

Here's two of my chassis fans connectors (there are 3-4):

Here's the connector that came with either my motherboard or the PSU, can't remember :)

I've never seen one of these strange cables before. All I know is that if I plug in the 4-pin mobo connector to either of these fan plugs, fans don't come on and don't show up in the BIOS. (Motherboard has a crazy awesome UEFI BIOS and shows you if it sees the fans.) If I try plugging the 4-pin connection into the mobo and the other side into the PSU, I can't POST. If I plug the PSU connector in without the mobo connector, fans come on.

What could I be doing wrong here? Is it a problem with the cable I'm using? Is there something I may have missed in the build?