I've installed v9.3 -- a fresh install, on a newly partitioned HD.

I have gone on line with it, using Firefox, and am pleased. The only changes I made were in some Firefox preferences, and changing the mouse to the left-handed persuasion and a different cursor..

Whatever I did or didn't do, the system is now inoperable. When it boots, the
mouse is not frozen in the center of the screen. Its buttons also do nothing.
The only way I could shut the system down (twice) was with the Reset button. Perhaps there was a way with the keyboard, but I don't know it. I was able to bring up a Process List (but I'm not sure how I did that); repeatedly pressing the Tab key moved the focus from field to field, so apparently the keyboard was operational.

There is nothing wrong with the mouse itself -- it works when I boot the machine to OS/2.

How do I get out of this fix?

The last time it booted, I watched the detailed progress on the screen. I saw
nothing tht looked suspicious, except one Warning near the very end, at the time when the network was being set up. I couldn't read it, and of course I can't look at the boot log.

I assume that I need to boot to the Fail Safe option, which I understand to be
a command-line mode. I am very new at this OS, and would much appreciate some pointers about how to go about diagnosing what is hanging the mouse and how to repair it.

You're the one!!!

For future reference, you can switch to a console by pressing Ctrl+Alt+F1. Then type 'dmesg' and look for any mouse-related messages there.

Do you perchance have a cat? An exceptionally large orange tabby is currently playing with my mouse... must be time for supper.

Seriously, if the device has not unexpectedly malfunctioned, the file that controls this behavior is probably named XF86Config and it should have information about the pointer device or devices, namely mouse and/or trackpad.

Nothing that you could have done as an ordinary user, e.g. in Firefox's configuration panel, could have (afaik) altered that file. Only root can twiddle with it. Sometimes you must kill the X process, again as root, in order to make it pick-up changes, but you don't describe yourself as having done anything like that. All that you've said that you did was to change Firefox preferences, operating as an ordinary user.

You describe this as a "fresh" 9.3 installation. It .. worked okay 'before?' Place to begin, then, is "before what?" What e-x-a-c-t-l-y...?

I had this problem but it went away -- I know not why. What you can do to start the mouse for that GUI session is:
Alt-F2 brings up run window
Enter "YaST" and it will start
Cursor down to "Hardware"
"Tab" to select device with cursor keys
select "Mouse" and hit return
The mouse will start working after YaST initializes it.