"Cannot close current program"-error when trying to swap content of frame

Can someone explain what this “Cannot close current program”-error means?

It seems to appear when I try to change the content of a frame from within th frame itself.

For example : when i have a frame in a frameset containing a page, and i have a button on that page to open another page in the same frame, then I got this error. When I point to another frame, or a new frameset, then everything works as expected.

It doesn’t seem to matter what I’m opening (uiws.openpage, uiws.editdocument, uidb.openview, … whatever)