What I mean by that is the video just kind of pauses while the game keeps going. It's not the engine being paused that's a definite, I've tested to make sure that's not it.
That means it can be a. a driver issue (most likely!!) or b. something with your graphics card(s) (unlikely, but plausible) or c. your motherboard might be dying on you (possible) or d. bad RAM (don't know how likely or possible that would be).
I'd reinstall the drivers and make sure to clean them properly first. Other than that, I can only say that I am using A6.60 all the time and never ran into rendering issues like that. On both ATI and Nvidia hardware and with or without shaders.
There are of course certain shader related commands that make a code act
differently on Nvidia graphics cards, but in most cases this shouldn't cause a freeze of rendering.
Cheers