Computer help forum: My videos stop in the middle.

Hello everyone! I am usually able to fix my problems by myself but this time I hit a wall! Most everytime I try to watch a video on the Internet it freezes in the middle. If I try it again, it freezes at the same place. If I close the window, go back to the same website and click on the video it sometime works. It does that on many websites such as Youtube, college humor, yikers.com etc...

I have high speed cable Internet connection and I can see the video is already fully buffed. When the video opens in Windows Media Player, everything works fine. I also noticed I sometime had problem seiing pictures as they would be in weird colors. I would be tempted to say my video card is the culprit, but since the movies play fine in the WMP and since I can play high graphic video games, it does not make sense to me.

Here are all the things I tried:
I downloaded the latest driver for my video card.
I used to use IE so I tried Firefox.
I disabled my firewall and my spyware protection.
I downloaded the latest Flash available.
I even reformated.

Here's some info about my computer:
AMD Athlon 64 processor 3500+,
2Gb ram,
Nvidia Geforce 7900gt/gto
I use Win XP.

I hope someone can help me, I have absolutely no idea how to fix it.