I still think it's normal, one core is hogged with mining, the other is doing system related tasks.
The system related task take 3-4% always when i'm not mining and so+i don't play any games that would use resources and so.
To be clear, does cgminer show 90% processor usage, or is 90% processor usage shown in total with cgminer showing 50% cpu usage? There are no system related tasks using processor as cgminer.
Why are we talking about cgminer here? This is the Ufasoft thread.