Is there anything out of the ordinary about the files or Layers?
Are Photoshop and OS fully updated and have you performed the usual trouble-shooting routines (trashing prefs by keeping command-alt-shift/ctrl-alt-shift pressed while starting Photoshop after making sure all customized presets like Actions, Patterns, Brushes etc. have been saved and making a note of the Preferences you’ve changed, 3rd party plug-ins deactivation, system maintenance, cleaning caches, font validation, etc.)?
yea! that worked!
i had tried the <ctrl-alt-shift> thing before, but i hadn't disabled the third-party plug-in. plus, i don't think i was as "quick-on-the-draw" as i should have been when Ps started up. once i was able to reset the preferences, all returned to normal.
thank-you very much for taking the time to respond, c.pfaff! \(^o^)/