Had the same problem as OP and others here, system would just shutdown randomly eventually through weeks of troubleshooting narrowed it down to the nvidia card causing the issue. As others mentioned in the post the problem is not fixable but there is a work around. I use the gfxcardstatus 2.3 app to force the os to only use the integrated video card. Some applications will force your os to turn dynamic back on and go to the nvidia card gfxcardstatus notifies you of this and you just have to click integrated only back on. You will noticed the screen change color a little when the cards switch. Pretty useful tool I'd say system runs 90% of the time smoothly but eventually crashes here and there when os force switches cards without you noticing. Also unfortunately you can't use the minidisplay port out to hdmi/TV anymore since that requires the nvidia card for 2nd monitor which will crash the system. It seems the nvidia card is being overloaded or something.