Opened files become modified (unsaved asterisk appears) without any modification
I'm working with file A, but I keep open the B and C files (either I didn't close those or I'm copying content from those), after some time B and C becomes modified (unsaved, the asterisk after the name appears). The Edit→Undo does not show any alteration (it's grayed).
May it be the problem that A, B and C belongs to a Book?
Livio Udina commented
Does this post describe your problem?