Woh woh.... Unless I missed something, I think I see your problem...
In this picture, you only have ONE molex connector (4-pin flat power) hooked up feeding to the PCIE. These adapters require TWO 4-pin molex connections to feed power to ONE PCIE connection as a single molex does NOT feed enough power to the PCIE. I saw a suggestion that you dump this adapter altogether and just use the two PCIE connections that come with your PSU, but I didn't read anywhere that you actually did that? Also, those molex connecters are notorious for having the pins pop out backwards from the ends, so they may look like they're plugged in, but the pins may actually just be pushed out the back of the connector.
I have to agree with Perineum though... I'd be really surprised if this is a fried MB. Of the few things this sounds like (incorrect power to GPU / CPU 8 pin not plugged in / grounding issue / hardware issue) I'd expect the hardware to be least likely. Especially considering it worked fine until you swapped a single cable.
*EDIT* And it appears that you've plugged the PCIE adapter on to the end of a fan or LED lead? These adapters MUST be plugged in directly to molex leads coming from the PSU, not daisy chained on the end of other leads in your rig as that could cause a fire hazard. (Although I recommend not using them if possible)
*EDIT 2* Reviewing the note on the photo, I'm not sure now if you're using this adapter at all anymore. If not, disregard the above I suppose. But I still have a hard time seeing it as a fried board. And you did say that you ensured the 8 pin CPU adapter at the top left of the board is plugged in, correct?