Youtube videos require Adobe Flash Player to run. Sometimes, for unknown reasons, the player simply stop functioning, which results in Youtube videos unable to play.
Often uninstall and install the Adobe Flash Player will solve the problem. Go to your Windows program manager, or Add/Remove programs in your control panel.
However, in some cases, you need to reset the player. Follow these steps:
1.Uninstall your Flash player: http://download.macromedia.com/pub/flashplayer/current/uninstall_flash_player.exe
2.Download SubInACL from Microsoft from - http://www.microsoft.com/...
4.Download the reset_fp10.zip file from - http://www.adobe.com/support/flashplayer/ts/documents/fb1634cb/reset_fp10.zip
5.Extract the reset_fp10.cmd file to C:\Program Files\Windows Resource Kits\Tools\.
6.Double-click reset_fp10.cmd, when it is finished you will see "Press any key to continue"
8. Download the executable installer for Flash Player from http://www.adobe.com/...
Now, try reload your Youtube video again. If this works for you, no need to thank me. This method does not come from me, just would like to share with those who are frustrated by this Youtube/Adobe program like me.