I had this problem occasionally while using Photoshop CS6 on my old laptop (a 2012 Macbook Pro running El Capitan, I think?), and now it is relentless on my new laptop (also a Macbook Pro, early 2015, running El Capitan). I cannot save a file. I've read that a lot of people solve the problem by hiding or removing clipping masks - but many of the files I create have no clipping masks, and the error still occurs. What's the underlying problem, and how might I solve it?