Can anyone tell me how to fix my Firefox?

[Karter Wood]

Hello, Yahoo!

I have had Mozilla Firefox for a while now and it has worked fine. Up until a week ago, it ran as good as Google Chrome does on my computer.
When I try to view YouTube videos, the icon on my task-bar begins to flicker and all the images in the browser come up with a shockwave problem.
The videos don't even load. I want to use Firefox as my default browser, but I can't do anything due to this.
Can any computer techs help me out?

[Gary]

Do what I did switch to Waterfox[ been using firefox for 7years] Waterfox is identical to Firefox for 64 bit computers only. It is faster, runs smoother, hardly ever crashes and all firefox addons work on it. It's a far better browser.
http://www.waterfoxproject.org/

[Chris R]

You probably just need to update your flash player. Download only from Adobe:
http://get.adobe.com/flashplayer/

There's an optional offer for McAfee Security that's easily missed. If you don't want it remove the check in the box.