Ive managed to reproduce the problem in a clean project containing just Playmaker, Particle Playground and the Playmaker Pathfinder custom actions (I dont even have any of the Standard Assets imported).
So it seems that there is some kind of conflict between Playmaker, Particle Playground and the Playmaker Pathfinding custom actions.
Hope the info helps any one in need or qurious about the problem.
I am sending the project over to the author of Particle Playground now so that he can check it out and maybe figure out what is going wrong.