I've had similar things happen. One day when I pressed the Windows key I got just a blank totally blue page/screen. Charms bar doesn't work but If I mouse down to the lower left corner and activate the metro screen there it opens fine. Then it works fine after that, for a while anyway. At random intervals it would do it again. I suspect its a video driver problem. It went away after a reinstall. It just recently its started doing something similar again. I'm just about ready to ditch my dual boot and go back to a Windows 7 only install. Desktop IE is acting up with blank pages and Outlook 2012 is also acting up with lags in displaying emails when you open them. In my case I'm pretty sure its the NVidia graphics driver that's the culprit.