GTX 570 SLI weird lockup/freezing issue . . .

[The_Dark_Abyss]

So I've had my system for quite a few months now (spec in sig) and I've had very few issues with it but recently I've encountered situations where when running in SLI mode, certain games would cause my first GPU to spike to 99% usage (while the second GPU shows 0%) and then freeze the game as well as lock up my system. This happens whether I'm using the overclocked speeds or running at default speeds. Anyone have any idea what might be causing this? It only seems to happen in games that are more graphically intensive (especially DX11 games like Sleeping Dogs or Max Payne 3) while games like Diablo III will run for hours without issue. This is happened ever since forceware 300 series+ of drivers. I'm not sure if it's an issue with the drivers or with the cards themselves. I'm also trying to avoid having to do a complete Windows reinstall.

In another somewhat unrelated issue, using the built-in nvidia HDMI audio output to my receiver seems to be causing certain games to crash while using SLI compared to using the onboard audio. Using the optical out also causes the same issue. A friend of mine had said that there has been a long-standing issue with SLI and encrypted audio output. Is this true, and if so is there anything to be done about it?