> Are you saying tha this isn't kosher, because the body of
 > save-window-excursion is not allowed to select a different frame?

I doubt it's kosher because if the old selected window is not on the
restored frame and a window on the restored frame gets selected, the
point of the buffer whose window is deselected is not stored in the old
selected window's pointm which is certainly not TRT.

Inherently, the source of all evil is the idea to have (1) these two
variables selected_frame and selected_window and (2) to allow setting
them independently from each other.

To avoid the present crash we could try something like the attached
patch (which does not try to solve anything but that crash).

martin