Safari 7.1 Update causing Flash Player Problems.

I installed the latest Safari 7.1 update and now my flash player videos are messed-up. I either see "HTML 5" or "FLASH" in gray boxes. This is especially a problem for me on YouTube because I can't multitask while watching a video. If I switch to another tab, the video stops playing. Also, the video player isn't YouTube's, with the usual options like "Play Later" or choosing the mid-sized screen.

I performed a complete, proper, clean install of Flash Player but this didn't resolve the issue. Is anyone else having this issue? Any ideas how to fix it?

OSX Version 10.9.5

Maverick.

iMac

Safari 7.1