If you're having problems viewing YouTube (or any other Website, for that matter), the first and safest thing to do is to try another browser. If that does the trick, go back to your favorite browser and clear the cache or "saved files." And if that doesn't work, try yet another browser until you find one that works.
Don't install supplemental programs unless you know what you're getting into.

Our staff at the women's center had trouble getting into their Web-based email. I couldn't solve the problem, so I finally gave in and called tech support. He gave me all sorts of solutions that didn't work, and finally we gave up. Then he suggested that I try another Web browser. That did the trick. I really like Google Chrome, but it's the fussiest of the browsers and can often have problems. Firefox is the Old Reliable, but even it has problems sometimes.

-Joe-