Stefan Monnier wrote:
>> I get crashes in org-mode when I do things in a region with invisible
>> text. I have not made any simple test case, but from my testing I can see
>> this:
> 
>> - There is something strange with the display in org-mode an items content
>> is hidden. You can position point after the three dots ... If you do that
>> and check (current-column) you get 0.
> 
>> - In code if you in org-mode do
> 
>> (while (my-invisible-p (point))
>>   (forward-line 1))
> 
>> until point is on a visible char and there insert an overlay with an
>> after-string it crashes.
> 
> Please make the "insert an overlay with an
> after-string" more precise, e.g. actual Elisp code.

It looks similar to this, I have not tested if propertize is involved:

   (setq ovl-str (concat "before"
                       (propertize "txt" 'face 'highlight-popup)
                       "after"))
   (overlay-put ovl 'after-string ovl-str)
   (overlay-put ovl 'display "")

See also the attached file. The crash happens in tabkey2-overlay-message 
if you let it take the path avoided right under the comment:

       ;; Fix-me: Emacs bug workaround
       (if nil ;;(tabkey2-invisible-p (1- (point)))


> Also, does it happen with any Org-mode buffer, or is the
> contents/setup important?

It does not seem to be dependent on the buffers content.

> Finally, please provide a backtrace.

Sorry, it is compiled with debug info, but there is no backtrace. It 
just crashes and MS offers to examine the crash. (This is on w32 xp.)

>         Stefan

PS: The attached file implements a way to handle Tab for completion.