Catalyst Version 12.10
AMD APP ADK Version 10.0.1016.4
1016.4 is the opencl runtime that comes included with 12.10. You need to downgrade to an older opencl runtime, and direct CGMiner to use the older version. Re run the 12.10 CCC driver installation, and completely uninstall the openCL runtime (you can leave the driver and everything else alone). Then install the APP SDK 2.5 from
HERE. Delete the .bin files out of your CGMiner folder, and see what that does for your performance.
If that doesnt work, I have an 8MB rar file with the 64bit opencl runtime files that you drag and drop into your windows folder. The installers don't like it much, but it works.