I can't say for sure when the dialog box first opens. It's definitely not when I start my computer or when I start Excel. At some point as I'm working I will notice that a new Excel "occurrence" has piped up. And it is just that dialog box. It doesn't announce itself by coming to the front when it first opens, it just lurks down there unless I make it the active window. So far today it has not made its appearance, but the last week or so it has been persistent in opening at some point.
What I mean by "When I have closed all other excel windows the Task Manager does consider this to be an active project, but even Task Manager cannot abort it", is that if I close all of the Excel files that are open, that dialog box remains and won't let me cancel out of it. If I open Task Manager it shows that Excel has one occurrence open and it is just that dialog box. If I tell Task Manager to make it close, it can't do it. Since it hasn't happened yet today, I can't show you a screen shot.
If I force it to open by clicking on the VBA Code Module, it does close properly when I cancel it, but I don't yet know if that will close it in the case where it has appeared of it's own volition.
I'll take a look at the link you posted
Thanks.