Grandpops, these tips for Adobe Flash (used for Youtube videos) may help:
1) Click here and make sure the option to "Allow third-party flash content to store data on your computer" is ticked.
Click the "Website Storage Settings" tab (second from the right), scroll down until you find Youtube listed, select it, then click the "Delete Website" button. If there are zillions of entries there then it may be less faff to use the "Delete all sites" option.
Restart your browser and try again.
2) Make sure you're running the latest version of Adobe Flash which you can get from here. Note that you'll probably want to untick the option to install the McAfee Security Scan thingy.
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