Why does Firefox keep freezing, then starting while watching YouTube?

I am trying to watch videos on YouTube, but every so often my whole computer will freeze for about 20 seconds, then the video will carry on plying for a few minutes, then it all freezes again. When it is frozen the video sound carries on as normal. I have the latest version of Firefox (4.0.1) and running OS 10.6.7. I have looked on software update, but there are no further system updates to download.

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).