I have been having the same problem and spent hours researching this. I finally played around with my flash settings in the specific video in ESPN I couldn't play and I almost feel silly for how easy the solution is.
At some point in the past year I restricted access to all websites so that they could not store any adobe flash info on my cpu. I adjusted my global settings and espn would still not run video. Same thing with many flash based gaming sites.
Here was my solution:
So I right clicked where the video or game should have been playing and realized I had the flash storage slider set at 0kb along with the box to never ask me again being selected. Once I adjusted the slider to 100kb and unchecked the box then the video began to work on the site. I did the same adjustment on the flash gaming site and it worked also. I only had to do this once per site.
Right click in the non playing video area and select settings, then things should look like this:
If your slider bar is down to 0kb and the Never Ask Again box checked then that is the problem. At least it was mine.