6
It could come from the RAM, but memory probs generally invoque a blue screen and don't make the puter freeze.
IMO, this one may more probably come from: the gfx card / the mb chipset / cpu probs.
So if you recently updated your detonator drivers or played with your config, try cleaning a little (find a tool somewhere to completely remove the gfx drivers, then reinstall).
Or, if your machine is a bit old, check the cpu fan. It may be malfunctioning, causing the puter to freeze randomly when the cpu overheats.
Skalpa.>