With MS OneNote installed, I could use the Windows + s key-combo to launch the screen capture utility. But it all of a sudden stopped working. According to this post, that "sometimes happens" and can be turned back on by toggling the checkbox lableled "Place onenote notification icon in the taskbar" (under File -> Options -> Display, if using OneNote 2010). Unfortunately this trick didn't work for me. (I.e., it didn't turn on the Notification icon in the tray).
I tried to turn it on manually in the Customize section of the Tray, selecting "Show icon and notifications" on the MS OneNote Quick Launcher, but was told "This icon is not active and will not be visible until it becomes active"