FFS! AMD & ATI, how F'ing hard is it to test the releases BEFORE releasing to the general public. You just made me waste 2h of my life on rolling back and getting in depth on what you guys managed to screw up so I could fix it.
So, to everyone else, here's the deal. The latest ATI driver and catalyst control center (11.5), they forgot to sign the driver for Windows (at least for x64, haven't tested the 32-bit), making it not to install properly unless you've explicitly allowed the OS to install unsigned drivers. And you should not have that option enabled anyway.