Premiere Pro :: Flickering Image Then Display Drive Stopped Responding

What I've done differently is applied a few effects to clips, such as contrast and exposure, and then nested the clips.  Then I've dragged these sequences together on the timeline and trimmed and edited.  The 13 minute video plays well for about 9 minutes, then it starts flickering, alternating with black and white screens, then in the last minute it crashes.  I get the message "Display Drive Stopped Responding and Has Recovered." I've begun replacing some of the nested sequences with the original imported assets, but still the same end result.

I'm working with 1920 x 1080 assests at 23.97 fps.  I've worked with these before, no problem (though I haven't had to add so many effects before).
 
I'm working on an Intel Core i7-3770 GPU @ 3.40 GHz 10 GB.