The Mbutton pan variable and right-click functions ceased to work this morning.
 
I have checked the setting - which is at 1.
 
I have also tried a different mouse which has the same problem.
 
What might have changed in the software overnight? Any thoughts on what I can do to correct the problem?

Did you first try rebooting the system?

I solved the problem!
 
I discovered that I had the ARE Practice Graphic Vignette running. When I closed out of it, the problem with the mouse went away.

Well that's a relief.  So simple too.  What is the ARE Practice Graphic Vignette?

It's the Architect's Registration Exam administered through NCARB. They developed their own CAD-style software - extremely simple and frustrating to use  - that everyone must use on the exam. You can download and practice on your own computer, which is what I have been doing.Well, it was a simple solution but several hours into the problem-solving. I took apart my mouse, thinking it was the problem . . . those mouse springs are not easy to put back, especially if they fall out before you see how and where they fit. So I learned a lot yesterday but lost a lot of work time.Thanks for your reply!