The most common causes of freezing and crashing are improperly prepared images and excessive zooming.
Here is a more thorough list of causes and solutions for freezing problems: http://help.videoscribe.co/support/discussions/topics/1000023738
(pay close attention to numbers 4,5, and 6)
and here is the official instant answers thread about the topic: http://help.videoscribe.co/support/solutions/articles/1000033705-crashing-and-freezing-videoscribe-free-pro-and-edu
-Mike (videscribe user)