Mine did that yesterday and this morning my console YLODed :'( I owned it for 3 weeks but it was a pretty early model. My advice if its in warranty, send it to Sony or take it to the store you purchased it from and they should either fix it or replace it!
Freezing in games, occurs when the processing unit tries to process to much data than what it can handle. It usually affects those games that have loads of action sequences or those that require a lot of charcter input e.g Sim games.
To limit freezing, after major action sequences, keep the movement to a minimum by having your character standing still for a moment; so the processing unit has time to catch up.
I worry about the freezing issue whenever I play on any of the Uncharted games, as there are things happening all at once on screen; also this problem is not limited to just products you know; it could also happen in humans too, when the brain tries to process too much info and panic sets in.
Lay off the weed.