Is Flash not installed by default? Downloaded FF4 and several sites won't display. Ex: Youtube says "You need to upgrade your Adobe Flash Player to watch this

Is Flash not installed by default? Downloaded FF4 and several sites won't display. Ex: Youtube says "You need to upgrade your Adobe Flash Player to watch this video." Other sites just don't work. Maybe I'm out of loop and need to update my desktop flash. Man, chrome has ruined me with its auto-updating.