My girlfriend and myself are having the same issues. Anyone else? I have to press the right button and put it in airplane mode and then take it out of airplane mode to get the menu to work again. I was powering the phone off and on again until I discovered the airplane method.
I am using the visible pattern for the screen lock. I redid the screen lock, but it still won't lock intermittently after screen goes black. I have to power off and on again to get the screen lock to work again.