Activate the mouse after a reboot which didn't activate the mouse?

[rhkramer@gmail.com]

Today I had to reboot my Jessie system, after Firefox totally hung the system 
(for over an hour, with 20 tabs open).  After the reboot, it seems that most 
things are working (well, the things I can test without a mouse), but the 
mouse is not working.

The Jessie system is connected to a KVM system, and because I had to run some 
errands, I started the boot process and then left, with the KVM set to the 
Jessie system.

When I came back and tried it, I found that the mouse is not working.  The 
mouse still works on the other two systems connected to the KVM switch.

I've tried googling and looking at (and trying some) commands found with 
apropos mouse or apropos x (a lot), but I haven't found a way to activate the 
mouse.

(I'm assuming that if I reboot and mouse around early after the reboot, the 
mouse will be activated, but I'd like to avoid another reboot, and maybe learn 
something.)

While I was looking for ways to activate the mouse, I did come across a place 
where I could click (well, via a keyboard shortcut) something that said 
something like: "activate mouse with KDE" -- maybe at some point in time I fat 
fingered something that unchecked that?

Anyway, suggestions appreciated.

I have tried to get to the "system settings" ahha, ok, I can type 
systemsettings at a CLI as user, but (1) I don't know how to navigate within 
that page to get to the mouse device, (2) but (on another system), although I  
see things to change about the mouse under Hardware ==> Input Devices ==> 
Mouse, I don't see anything that appears to activate (or de-activate) the 
mouse.

Suggestions appreciated.