Lately, when I launch InDesign, a dialog box immediately appears that reads: "You cannot reverse this change with the Edit>Unod command. Do you want to continue anyway?" (see screenshot) and you only have two choices: Cancel or OKAY. Being forced to choose OKAY, I'll open a Recent file of some sort, and the stupid dialog box follows me there as well, and sure enough, if I make a change and go to Command Z (I'm on a Mac), the Undo command is ignored and in fact Edit>Undo is greyed out in the menu bar. This has GOT to be a bug, right? I have figured out an annoying way of going around the problem. I'll make some tiny change — like adding an extra period at the end of a sentence and then deleting it — and then choose REVERT, after which time the issue seem to resolve itself. Again, it only seems to appear upon the initial launching of the program.