Why does Storyline often quit unexpectedly?

Thanks Peter, i think i might have found (and solved) one of the problems. I noticed that when i copy and paste an image ( especially from the internet) that Storyline will hang to the point where you cant even save your work and after a while.... quit. 

So i had to go into every slide (there were 45 for this particular project), right click the image and then click 'save as picture' to somewhere on my hard drive. After that, we were back to normal speed instead of taking 2-3 minutes for a change to happen or even move to the next slide. 

Hope this helps others who come across the issue.