they are locked for a reason..
They are defective core (that not pass QC)..
So it not strange it fail at some point....
edit: btw what do u means by 3D movies?
If your player support multi core control, try set it to only use one/two healthy cores.... (or set affinity in task manager) it's temporal/turn around fix..
if its unstable how can it run crysis 2 in 3d mode?