I installed TP 5.1 in Max 2013 64 bit and Krakatoa seems to render the particles. Is it possible that you don’t have the “Thinking Particles” button in Krakatoa’s GUI selected? If that’s not the case, please let me know what sort of error messages you get. Ideally you would drop a PositionBorn in a fresh scene and confirm that those particles don’t render either.
[attachment=0]TP_51.png[/attachment]