Recently I have started having a problem that when I try to play any flash videos such as Youtube, it will buffer completely but still stall every few minutes in the video. I'm not sure what it is. I have updated all of my software, etc.

Here are my machine specs, I'm sure my machine is not the problem.
MacBook Pro
OSX 10.5.8
2.26 GHz Intel Core 2 Duo
4 GB 1067n MHz DDR3

Firefox version 3.5.5
Shockwave Flash 10.0

Please help!