A popup context menu containing "Remove from Group; Clear Group; Group; Group Manager; etc etc" comes up on left-clicking the "mute" button on a track, also on the solo button, also just clicking somewhere in the track.   
 
beginning to investigate other options here, x3 seems awfully awkward

I get those menus when right-clicking on the buttons. The group options are very useful. Not sure why left-click causes the context menus, unless the left/right buttons are switched in windows.

scook
Not sure why left-click causes the context menus, unless the left/right buttons are switched in windows.

Agreed...check the Mouse section of the control panel. AFAIK there's no preference in SONAR that allows switching the left and right mouse buttons.

I think I must have gotten sonar into an unstable state somehow, that problem went away by itself.

Right

williamcopper
I think I must have gotten sonar into an unstable state somehow, that problem went away by itself.

If so, nothing like that has ever been reported before. AFAIK what associates a gesture with a particular mouse button is a Windows function.
 
In other words, I think it is extremely unlikely what you experienced has anything to do with SONAR, regardless of whatever you may have done within the program. As a result you will probably run into this issue again, possibly with SONAR or possibly another program. If the right and left buttons didn't become reversed within Windows, then I would check whether your mouse is performing up to spec.
 
Also be aware that some mice have applets that have their own preferences and that could be a problem. For example if you have a Logitech mouse, look whether an applet is present and if so, click on "restore defaults."