I cannot watch videos on YouTube, although the connection is OK? Can you help?
May be you should update your Adobe Flash Player plugin? http://www.mozilla.org/en-US/plugincheck/ At this page you can check your plugins are up to date.
If the connection is OK, download and install the latest version of Adobe Flash Player. Before beginning the installation process make sure you close the browser. Also, press Ctrl + Shift + Delete key combination and clear all cache, cookies and temporary Internet files. If the problems persist, update the browser to the latest version.