I'm no expert, but if the video is completely buffered/loaded it may be something with your computer, possibly your browser and or version of Adobe Flash Player. Should just be a software problem, can't see it being a hardware problem unless you have a 15 year old computer.

What browser are you using? You may want to go to http://www.adobe.com/support/flashplayer/downloads.html and get the newest version of Adobe Flash Player.