Internet video making computer run slow


MacBook Pro 17"
Version 10.4.11
Processor: 2.16 GHz Intel Core Duo
Memory: 2 GB 667 MHz DDR2 SDRAM

I am having a problem where when I try to watch a video on the internet and my computer starts to go very very slow. Whether it be on youtube or or any other sites. The audio sounds fine, but the video is all choppy or sometimes doesn't play at all. The computer then becomes very slow and un responsive for a little while. I updated to the latest version of Firefox, Flash, and Java. I barely have any other programs running. When I play a DVD on the computer it runs fine.

Also, my internet seems to run kind of slow, where as with my desktop (Win XP) it runs fine, as do the videos. I am running off of a cable line as well...

If anyone has any ideas please let me know.