I'm not the "tech support guy" but I am wondering if you right click on the video player and then click "Settings..." on the menu that pops up, then check the "Local Storage" tab on the bottom of the settings window (see attached picture). If this is set too low, it may not be allowing the video player to buffer the entire video or buffering it incorrectly or something..

Like I said, I am not the tech support guy.. just offering a suggestion. You should be able to set it to 10MB or unlimited. The setting only applies to the site you are currently connected to.

Also, make sure you have the most up to date version of Flash Player installed on your computer. You may need to completely remove the old installation and install it fresh if installing over the top of the old one doesn't work.