I don't know what happened with Firefox. I've been surfing the web since the morning and suddenly when I try to access some pages I previously viewed it doesn't load all the content because it's lacking some plugins.
Firefox says that "some plugins need to be installed" and when it tries to get them it just get stuck. But the weird thing is that I don't know why this is happening and a few hours ago I could easily have access to all this pages I'm having trouble now.
This doesn't happen when I use IE. What's wrong with Firefox or what did I possibly do for this thing to happen?
For instance, I can't watch CNET's videos because it says that I need to get Macromedia Flash when I already have it installed in my PC.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic