Freeze on playback

On occasion when I am editing a piece and moving notes up or down on an orchestral score, when I try to play back what I've edited, the playback line freezes or moves at such a snail's pace, I am forced to save the work, then exit and re-start the program. After re-starting, the piece plays just fine.

II tried hitting the ESC button, but that does not help, nor does anything else. What is the fix for this?