I have initiated this thread and wanted to point out that I simply
went on and use ULTRAEDIT to edit the source code now, instead of the
built-in MPLAB editor.  It's better anyway.

Unfortunate though that MPLAB doesn't accept the F10 key (make project)
in its programmer window, which sometimes happens to become active
when switching from ULTRAEDIT to MPLAB by the ALT+TAB shortcut.

But I can live with that :-)