When on the Internet any videos are shown on the page as a gray square with
a "PLAY" symbol centered in it. When I click on it, all I get is a black
square. Am I missing a plug-in? If so how do I attach it to Firefox?

I am using an Acer Aspire One. Intel Atom 1.8 G processor, 1 Gig memory, and
Ubuntu 9.04 Netbook Remix