Screen Saver fails

I have a new Dell laptop with Windows 8.1.  I set up the screen saver to show my pictures, but I sometimes get the error message: "An error is preventing this SLide SHow from playing."

I usually can go to my screen saver settings and modify something and then it will work again, for a while.  Then the error message reappears.

Any thoughts on what I need to do?

Thanks,

Mike T in VA.