No video with Firefox 3

I just downloaded Firefox 3 and cannot watch video on myspace, youtube, etc.......Everytime I try to watch one, it says "you must add the following plug-in"..... Installation says "successfull" but still no video..... I see others having this issue...Is this a Firefox 3 problem???? Anyone know an easy fix????

IS this related to your flash question?

download the appropriate plug in and install it. not all videos are flash