I would start with your USB controller as well, since you've already have this unusual observation. So try updating your USB controller driver and do visual check the capacitors of your components.
Good luck.
After my bad experiences with Asrock, during its introductory days... I never think of building a rig with asrock. I would like to give benefit of the doubt for the supplier. It may be the supplier that gave me faulty boards.
Guess your video card need re-seating. Try opening your computer box and remove/install your card. you may also try cleaning its contact.
Worst part is the card is failing. Hope this is not your case. :(