Uh, your SYSTEM ram (the 6 gigs of ocz) you have is 1600 mhz. That has NOTHING to do with your video memory. The video memory on your card is set to 1100mhz. The two are separate from each other. The 1100 mhz is what your video card memory is set to and is the default setting for your card.
The Catalyst Overdrive program is ONLY for your video card where you can over clock the GPU and the video memory speed. Did you set your video memory speed to 1600 in the Overdrive program? If so, that's definitely why you are seeing pizza slices (also known as artifacts). That occurs when you've over clocked your video memory and/or your GPU speed too high. You can go back into the Catalyst Overdrive program and reset your GPU and memory settings back to their defaults. I would suggest you do this and try running your game again.
Also, with you having over clocked your video card too high, it might be overheating as well, causing the hanging.
If you've done any other tweaking within your bios, I would also suggest you reset them as well to the defaults and then run your game.