I have had exactly the same problem for ages and i have just solved it! If you go onto the flash installation and then it says ' if the flash player fails to install then please visit the adobe website to help troubleshoot the problem' you then have to click on the link and then one of the options tells you to make sure you have unintalled previous flash players, so you then click on this link, uninstall previous flash players, and then download the flash player again... and bammm it worked for me
and now my youtube is working.. i hope it works for you
xxx
