Alright in my Case, ( http://www.youtube.com/watch?v=DjpN5HoX8xA )
What I have gotten to fix this was disabling (in device manager) my 4th physX GPU. That by itself wasn't a total fix, as there was still some flickering in puddles and some massive FPS dips/mouselag near soem light sources.
This second problem was fixed by using SLI compatibility bits of 0x42506405 in nvidia inspector under crysis2 profile. (thanks Blaire from nvidia forums)
Now my game seems to be running well finally, 120 FPS and no random slowdowns, flicker, or glitchy motion-blur!
Will keep playing to make sure, hope this info helps you somehow crytek