Which same issue? Not using the GPU? How are you checking the usage - Task Manager does not, by default, see Iray/CUDA activity. Is the GPU l;isted as available in the Advanced tab of render Settings, and is it checked? What driver are you using (right-click on the desktop>nVidia Control Panel)? How much system memory do you have? Have you tried a really simple scene, just a primitive (Create>New Primitive)?