I got it fixed (that was fast
I was chatting with some folks in IRC about it and was led to opening Control Center, KDE Components, Session manager and click to start with a blank session. Then logged out, then back in. No error message! So I had to restart a couple system tray icons (like the mixer, post-it notes, etc.) and then back in KDE Components I selected to restore a manually saved session. After being sure everything I don't want open was closed, I went into the KMenu and saw the "Save Session" option and clicked on that. Logged out and back in, and everything is fine. No error messages!
So if anyone else gets in this pickle, that's how I got it solved, thanks to folks in IRC, of course...