Thanks, guys.
1-Yes, restarting Sonar fixes it, so it is an inconvenience but not a disaster.
2-There were no overlapping clips in this case, but that is a good thing to watch for.
3-I don't really know that this has anything to do with a split soft-synth track, but it is a theory I am considering.
4-I will try the Pic Cache thing next time.
I appreciate the help. If this is the worst issue of 2015, I am good.
By the way, the sunglasses in my picture are to protect regular mortals from looking into the eyes of The Mighty Konrad. You fellow Sonar gods should be safe.