I have had this happen to me twice now. I'll be in the middle of working on something that has resulted in me not rebooting my machine for several days. If Windows 7 is waiting to install updates ...
I installed updates via Automatic Updates (I have it set to "Notify but let me choose which to install"). Then I rebooted as prompted. Immediately upon logging in I received the message "You must ...
I like Windows to keep itself up to date via the automatic updates, but sometimes it does that when I'm not at the computer and it's doing something critical, like downloading the latest stack ...