Shockwave/Flashplayer problems

I've had enough of this problem, basically anytime I try to watch youtube videos, and most of the time when there is flash content on the page, the browser crashes. I've got IE 6.0; Firefox 3.0.4; and Google Chrome and they all do the same thing and either crash altogether, say that shockwave has encountered a problem and closes those down only. Occasionally the computer reboots itself. Whether or not it's related, other programs I have crash as well at times - Windows Media Player 11.0; Picasa 3; Nero Wave Editor 3.5.4.0 and Microsoft Word.
Any help would be most appreciated, cause as you would expect, it gives me the shits.

Any help would be most appreciated, cause as you would expect, it gives me the shits.

