Quote Originally Posted by alphanumeric View Post
If you have it set to sleep after x minutes, it may be going into sleep mode while the lid is closed. And because the lid is set to do nothing, it stays in sleep mode until you press a key.
Just to be clear on these points, changing the power option from "Do nothing" to "Sleep" on closing the lid resolved the problem of the blank screen on reopening the lid, necessitating a restart. I don't have an option set to sleep or hibernate after x minutes. I hope this helps anyone who has encountered the blank screen after installing the Creator's Update.