There is an element of truth to this one - an attack was discovered which took advantage of data remanence in RAM, allowing an attacker to grab data from the RAM in a machine. There was a very short timeframe (a matter of seconds or minutes) in which to do this, but it wasn't a hack of the PC as such.

Simple Wikipedia link to [Cold Boot Attack here][1]


  [1]: http://en.wikipedia.org/wiki/Cold_boot_attack