Same problem here.
Start with stabil FPS, after 1min the FPS is going down. After a while, the game stops (no FPS).

System:

• Windows 7 Professional 64-Bit
• CPU i5-3570k 4,4 GHz
• 2x GTX 670 SLI
• 16 GB DDR3 RAM

Still have the issue when i set the speed of the CPU to the standart (3,4). So it`s not an overclocking problem.

GPU 1#: Start with 60% Power. After 10 sec. it starts drops between 30-60% Power. The FPS is going down, the power is still going down, after 2 min the GPU don`t make anything. -> Game freezes.
GPU 2#: Don`t make anything.

RAM is now really funny. It`s always increasing! Nothing works, but the RAM is go up and up...

#Question: Is there anybody with a ATI/AMD GPU here, and have the same issue?