It happened with me, when I turned on Switch Control. As soon as I turned it on, I was not able to click the box I was supposed to. After depressing the home button four times, it closed, or I thought it had. When the phone went to lock screen, I couldn't get it to unlock for several minutes, no matter what. It released on its own. I did a refresh restore, once I could get back in my phone, just to make sure everything was as it was, before I had my problem.