I'm having an issue with Firefox. Anytime I try to play a video on YouTube (or an embedded YouTube video on another site) my browser becomes unstable. The video is jumpy, going full screen to window takes a while and changing/closing the tab or pausing the video can sometimes take over a minute. This seems to be a recent issue with Firefox 35. Chrome works fine, although I much prefer Firefox as a browser. This happens both when I'm using HTML5 or Flash (libflash version is 184.108.40.2065) as the viewer on YouTube.
I'm running Ubuntu 14.04.1 64bit with version 331.113 of the proprietary nVidia drivers. Any ideas?