Similar to here, I’ve been receiving the “Please Wait… Updating toolbars” … window every time I open an instance of Rhino (7.16.22067.13001, 2022-03-08).
I got it to stop by disabling the Read-only property of colors.txt, thus allowing it be overwritten.
While Read-only was enabled, my custom colors were preserved, unlike here:
I use Rhino from multiple Windows user accounts on my Windows 10 PC, and the latest Rhino may have been installed by another account. This may have contributed to the repeated updating.