Help!

My 360 has decided to ruin christmas by being a muppet.

It starts out ok, lets me log in, start games, navigate menus, watch any cutscenes, all ok.

As soon as I move, or sometimes if its being particularly annoying, lets me play for a bit, or press the rt trigger, it freezes up and crashes on me.

Any Ideas on what is causing it? It isn't limited to certain games, isn't limited to either online or offline play, and i don't get any red lights.


Bollocks.