A c0000005 exception codes is a memory error. Do you see any of these in your event log other than from Crysis? Even if you are not OC'd you might have a fault that only shows itself in MWLL, like it stresses that component just the right way where it cases an error. As an example I can purposely make my memory unstable to where MWLL will crash with 'c0000005' errors after 20 minutes, but vanilla crysis and pretty much anything else will run just fine for hours, even days.
Also If you are running your ram at 1600mhz you are OC'ing something. An x58+i7 are not rated for that speed. Yes some i7's will allow you to do that, but some won't. My i7 needs to run out of spec to run my memory at 1600mhz. I have a feeling that if are running your ram at 1600mhz, something is not correctly configured dealing with your memory controller or ram and is causing the 05 errors.