I could not duplicate it on any of your projects.
I'm gonna bet you had a "nag" dialog pop up, but it was off screen (or on a 2ndary monitor that you did not notice?)
We addressed one nag dialog that had this misbehavior.
When you opened an empty project, when you went into "edit mode", did any message boxes ("nag" dialogs) show up anywhere? If so, do you remember what it was about?
If this does happen again, just hit the ESC key, which should "dismiss" the misplaced "nag" dialog. You should then go into Edit mode just fine.
