I fixed the problem by uninstalling the day 0 Windows 8.1 updates. The one that did it was the update that took a while to uninstall and the progress bar hung at like 99% for a few minutes. Be sure to hide the update under Windows Update or it'll just autoupdate again. Enjoy a super stable tablet afterwards!! I hope Microsoft realise this and fix it up with another update. They're usually on the ball!