In 40 years of working with mice and computers I've never had one just quit.  Everything was fine and then no mouse movement.  My first thought was something in the background was running and stopped the mouse.  I logged out and when it came back, still no mouse.

I noticed the light on the mouse wasn't on so I tested the batteries and each had only 1 volt.  After I replaced the batteries everything was fine.

In all this time I've never had a mouse just quit without warning.