I normally position my toolbar at the bottom of the TCMD window and wondered if maybe the problem arose only in that case. So I moved it back to the top (default) position.
Then I open the options for TCMD and change the setting for "Lock tabbed toolbar". After I click OK to return to TCMD, the toolbar has vanished completely. As I wrote earlier, it is as if I issued the
tctoolbar /c command to clear it.
The command tctoolbar /i restores it, so the data does not get removed from the INI file.
Oh, one additional clue. My TCSTART script loads the toolbar from a file when TCMD starts. If I comment out the commands that do that, TCMD comes up with no toolbar. It does not load it from the INI file.
Now I was looking again to see if there was an option for loading or not loading the toolbar defined in the INI file. I noticed the margins settings on the "Windows" tab and made a change. When I clicked OK, the toolbar disappeared. Now it seems that any saved change causes the toolbar to be cleared.
The toolbar was not cleared in previous versions of TCMD. I can live with the current behavior, but it is peculiar (especially if no one else is seeing it). I'm away on a trip at the moment, so all of this is being done on my laptop. If I were at home, I would have other computers on which to try it.
I tried some experiments with TCMD35. I could not test whether the toolbar would be loaded from the INI file because the data is not stored in the INI file for version 35. I figured out that the "Tabbed Toolbar" options screen would let me save the toolbar, so I did that. Then I closed Take Command and looked at the INI file. The toolbar data is now stored there. However, the tctoolbar /i command does not load it the next time I launch TCMD35 (nor does the toolbar automatically load from the INI file).