Ok, first of all, i am not sure that VLC crashes firefox. Maybe, maybe not.
But, a lot of times i tried to go to a page with an embeded video, firefox would die.
So, i go to download the videos, and open it, and they open wierdly
Take a look at the screenshot

i have no idea why there are three windows.
The movie itslef plays in the right window.
These are movies from http://www.mozilla.com/press/mozilla-2006-04-27.html
Other AVIs i have on my PC play just fine.
Thanks for the help in advance.