I have the same issue with my CPU usage being extremely high. I am running a 5770 on an AMD X4 and it uses up a whole core to keep up with the miner. Is this a problem with the Catalyst driver? I really don't know what else it could be.
It's the Catalyst 11.7 Whql...The 11.6B should fix the issue.There is no need to uninstall the 2.5 APP runtime it is just the Video driver not the OpenCL variant.