I installed 8.x using the built-in updater of 7.x. After installation everything seemed fine, but then I tried watching a YouTube video. This caused both my browsers (IE 10.x and Fx 19.x) to freeze. When I upgraded from 6.x to 7.x I had the same problem, but that time I was having problems with all Flash videos. This seemed to be caused by the combination: Flash & Online Armor Free.
Windows 7 Home Premium x64 SP1 - all essential updates installed
Flash 11.6.602.171
Online Armor Free 6.0.0.1736
Lucky for me, I made an image before installing 8.x. I will not upgrade until this problem is solved...