So lately I've had this problem occur a couple of times in Premiere Elements 12, where in the middle of editing, video clips will pause randomly and when pressing play again, they won't play. I had to restart the computer last time it happened but now it happened again almost instantly. Not sure what to do. I recall this happening before but at least then they would play again in a short while. Now nothing.
What are your computer specs?
How much RAM and how much free hard drive space?