Bug: All PopUp Windows (frm's) Stop Working

I am about ready to do a clean install of Rhino, but wanted to check and see if any McNeel folks had a fix or wanted some debugging info before I do.

Rhino starts off fine but at a certain point any popup window stops showing (aka frm.Show()). It happens within an hour or so, but I can’t discern a rhyme or reason to it. All of the sudden clicking this does nothing:

Nor does my middle mouse button popup toolbar. Commands with dialogs show nothing and terminate before doing anything. These curves were not lofted, but a little white box did appear:

It disappears as soon as I rotate the viewport.

All commands work from the command line, but the way -_Save works is a bit troubling. I can only save it as a one word file name (space bar completes the command) in the default directory (browse does not work as that would be a popup window).