Well the only way a link could start playing a movie and stop your keyboard or mouse from responding was if there some sort of malware attached to the link which prevented you from you doing so. Surely you have heard of malware?
It's usually people bashing keys in a panic that makes them think they can't close it when they can probably close it quite easily with a right click or pressing Esc.
Chief got me while in work once with a link to gay porn, it was something on the Man Utd board about Beckham and I clicked a link and got full page porn.
Mate stop right now, I'm an IT manager ffs. It wouldn't be malware anyway, it would just be a script that the page would launch. Would that stop you from turning your monitor off? Would that stop you from locking your screen? Would that stop a Ctrl + R? Nope, so jog along you silly little noob
I'm sorry! I wouldnt have said anything if i'd known. My commiserations! EDIT: Also yes, I am aware that there is no script or malware that could prevent you from just pulling the plug out of the wall to shut the computer down, you bellend But most people are stupid as ****.