Strange font-lock/invisible/intangible bug

[Damien Elmes]

Hello,

I've been trying to debug some weird behavior with emacs-wiki.el on
the nearly-latest CVS (as of about a week ago). emacs-wiki.el uses font-lock
mode to convert a string of the form "*foo*" to bold, in the process
propertizing the "*"s as invisible and intangible.

Now, there is a difficult to reproduce bug in the latest CVS which wasn't
around in previous emacs releases. Sometimes (maybe 1 in 20 times?), when
typing "*foo* ", point is suddenly moved to the line below. Infact, not just
space, but any command - Even C-x =, which you'd expect to show no character
(as I'm at the end of the buffer), instead says "C-j" in the minibuffer and
point is suddenly moved to the start of the next line. Repeating C-x = now
indicates that there's no character on point.

The other strange thing is that pressing backspace a few times and repeating
the same key combination results in it working. But if you undo the previous
line instead, and type it again, the strange behavior results.

Does anyone have a 'hunch' on where this bug might be, or any tips on how I
might debug where this is going on? My C knowledge is somewhat rusty.

Regards,
-- 
Damien Elmes