Just out of interest for people experiencing SLI freezing issues, my issues 'appear' to have disappeared with the release of the 177.x and 15.17 drivers. I have managed to play for long periods of time without any freezing at all, the system is rock solid at the moment (I am running 177.39 with the PhysX drivers as well).

My settings are :-

NB=1.46v
SB=1.50v
Memory (OCZ 1333 Reaper HPC, 7.6.6.18.2T with 60trfc) = 1.86v
CPU=1.1v (I am not using LLC due to it falling over with that enabled).