This has happened once before but I have forgotten how to get rid of it. On a rare occasion, a small red dashed box will appear on my 2-D drawing. I can't select it in any way to delete it. It's like it is on another layer. When I close and re-open the drawing file (even after program shut-down) the box remains, but gets larger with each file re-opening. I have TC Professional 17. Any ideas on how to get rid of it? Thank You!

That red box shows your current Workplane. Toggle it ON/OFF via View>Display>UCS>Display WorkPlane.

Henry H

One way you could accidentally show it, is.  If using the default right click menu in 2017, on the left hand side of the right click menu on the workplane line, is 'show / hide workplane'. quite easy to catch this by mistake.