While likely not the issue you should do this for now:
1) apply any BIOS firmware update to your motherboard
2) set CPU and RAM to stock speeds
3) run MEMTEST (or type "memory" into the Start Menu and use the memory diagnostic tool)
apparently some games run better with one GTX670 used for the main game and one dedicated to PhysX rather than both in SLI. It would vary by the game. I suspect Borderlands 2 would run best this way rather than 2xSLI.
Also, due to micro-stutter (which is not your red-black issue) if a game will run at 60FPS on a single card do so. No need to remove the second card physically.
There are MANY games that hit 60FPS with a single GTX670.
- single GTX670 mode if games hit 60FPS (max quality or close)
- single GTX670 + dedicacted PhysX 670 if a PhysX game runs better that way
- 2xGTX670 SLI for very demanding games that run better that way (microstutter but higher frame rates)
- again, it's pointless to 2xSLI if a single card hits 60FPS as you introduced micro-stutter but gain no benefit as your monitor 60Hz refresh (60FPS) is already maxed.
Thanks for the list of things to run through. Been working on my new rig all day, and I've got class in the morning so I'm going to have to wait before I attempt to try any of that. I'll update with results tomorrow evening.