you need HWMonitor ... it will show you what amount of memory is being used on your card, you maybe exceeding the 2GB on your card, and its putting the overflow onto system/pagefile. - try turning down the details to minimum? still freeze?
Is your swap/pagefile system managed? or did you set it yourself?
I always set my pagefile (i call it swapfile sorry) to: (system ram x 2) + graphics card ram. eg if i had your computer, i would be setting it to 12+2 = 14GB. sounds large right
but if your computer cant clear enough memory by dumping to swap/pagefile, then it usually grinds like a trooper or misbehaves. maybe that will help.