I currently have Windows 7 ultimate 64 bit. I've updated everything and for some reason every now and then the taskbar will crash. If I have a program up it will be still be openign and running, though if I move my arrow to the taskbar, I get an infinite blue spinning "loading" circle. If I hit contorl alt delete, the PC will in fact bring me to "Shut down, task manager, log off, switch user" options, and if I select task manager, I again get a blue spinning circle in response to moving my arrow over it. Nor will any arrow/tab/enter keys work.
This seems to happen by just leaving my PC on for every 1-3 hours.