I was having an issue playing imbedded Youtube videos here - the video either stays black or just sits there loading. I tried a few at random on Youtube with the same result. So I googled around and found it is a known issue with Firefox v 21 and 22. I've got FF v 22 and Shockwave Flash version 11.8.800.94. One of the sites I Googled said to turn off the Firefox Crash Reporter. Sounded dumb but it works! If you have the same issue you can turn it off at Tools>>Options>>Advanced>>Data Choices and untick Enable Crash Reporter. You may have to restart the browser for it to take effect - I did. However, this seems to be a hit-and-miss fix as it sometimes works and then will not again on the same video. Anyone having a better fix feel free to let us know.