The symptom is that the system (presumably the Explorer.exe process that runs the shell) becomes either partially or completely unresponsive to most user input: Right-swipe to launch Activity Center (and get to all settings, etc.) stops working; You can't
type at Cortana in the "Ask Me Anything" box, and the Windows Button itself becomes unresponsive. In the past, I've seen that all "Modern" Windows apps stop working - I don't know if that happened yesterday, because I try to never use Windows (Store) apps
anymore, only Desktop programs, as the apps seem to significantly destabilize the system. (not to mention that most apps are lobotomized in the first place. OneNote is the only app I normally use, but I had the desktop (OneNote 2016) version opened when this
happened again yesterday.)
Interestingly, the Start button is completely unresponsive EXCEPT when you right-click on it, where you can at least still get to the menu to shut down and restart. (I think this may be evidence of one of the seams showing in Win10: That part, which is
there to provide access to the "old way" of doing a lot of Sys Admin functions, is still actually running in Desktop mode, not as a Modern app...)....
Are you using Chrome to browse? I have noticed that Chrome tends to introduce little freezes to the system, including the start button, taskbar ect. In fact sometimes I have to exit chrome to get the system moving again. I've found notifications not popping
up as well. I only just installed chrome to try out the new .50 version and immediately noticed all the unresponsive behavior.
I don't get these problems with firefox.