You Tube videos also do not play on major websites such as that of the National Post. As the videos play in IE and not in Chrome, it seems logical that at least part of the problem, if not its origin, lies within Chrome.
Fixed. When Chrome installs a new version of any plugin, the plugin is automatically disabled. For why is peculiar. To remedy, go to chrome://plugins, and enable the new version. In this case it was Adobe Flash 10.
The answer was derived from a forum post that dealt with Chrome’s deficiencies in effectively handling plugins, and this particular solution considered through analogy.