I checked the code of `org-insert-heading'.

One potential factor: when folded, and putting cursor and the end of
heading, the cursor is supposed to be

:END: (here)

and it's not judged as a heading.


On Tue, Apr 23, 2013 at 2:57 AM, Bastien <bzg@gnu.org> wrote:

> I'm tempted to apply the following patch, as this problem falls under
> the category of "inserting in an invisible region".  I don't think it
> breaks any non-interactive call of org-insert-heading, but this needs
> further checking.
>
> Also, note that the problem occurs only when there is no blank line
> between the :END: and the following headline, so maybe the real fix
> has to be within org-insert-heading...
>
>
>
> --
>  Bastien
>
>