Video only plays when mouse is moving

I have a MacMini (Mid 2011) and it seems that out of nowhere this problem started. My videos become choppy, then halt unless I continue to move my mouse. In order for me to watch any type of movie, I have to keep my mouse moving the entire time. This problem only started recently, before that I never had any problems at all. Secondly, my ability to watch any type of Netflix video has ceased. I get a weird error message - again both problems only recently started. The first seems to be linked to around the time that I downloaded Yosemite, but the Netflix problem only recently...

Note I have 3 monitor for my display (not mirrored) and again I have always had this set up and never had the problem before.

Please help.