I had the same problem on a GTX680 DirectCU-II
The GPU was overclocked by factory and gave me this issue. Max temp 70° and crashed.
I try to "downgrade" the frequency of the GPU from 1200MHz to 1000Mhz (the standard one) and had no more freezing / crash issue.
Another thing that i notice is the...
I could give you my obsession with everything that belongs to the world of "the witcher" so I would not longer need to collect all those wonderful gadgets and you could keep the whole ultimate pack and also my small trouble :D