I wonder how this survived so long in Blender... (2005/03/09 commit).
Reason was the call to BPY_free_screen_spacehandlers(sc) in kernel,
which was freeing up scripthandlers in a weird way. That call is
really obsolete. The real freeing should go in the del_area() call,
to prevent copying and deleting area in the UI to go wrong.
(Crash happened in testing timeline markers, and holding CTRL+Uparrow
a while...)