Here is exactly what happens.
I pick the video on youtube and as it is loading(the bit where the little circle is going round and round) it just stops, crashes or whatever. I can hear like a click sound, like the noise you hear if you click on a link or something. I click on the page and it says in brackets at the top, Page not responding. After around 4 or 5 mins the video actually begins to work again but then crashes again and then after another 4 or 5 mins it starts working again. PS The webpage temperarily crashes, not the PC itself.