Same symptoms in Win7 this AM. It took me down for 3 hours. Finally restored an Acronis image and all was fine. I'm sure by that time they had the fix in the pipeline. As with Mac, my problem started when I was in Palemoon and stepped away for a few minutes, only to find a script error message on the screen. Then slow as molasses and black screens. I had to do hard shutdowns too. Figured I was somehow infected. Instead I was apparently infected by the very thing that was supposed to thwart infections. All good now.