Hello, I have this strange problem with my n9.
Almost every time the alarm goes off in the morning, I can't shut it off. All I see is the lockscreen with a wallpaper (no blue swipe bar visible) and nothing is responsive. I can't swipe the screen and non of the buttons work.
I have to put my phone under the pillow and wait for the alarm to stop, then everything works fine.

I can't reproduce this problem intentionally, it only happens in the morning.