progn: Search failed: "^\\(.+\\):" when replying

[Sébastien Vauban]

Hello,

For a long time now, I've a (very annoying) problem with *some*
messages when replying: instead of inserting the original mail
prefixed with `>' characters, it just shouts at me, telling that
`progn: Search failed: "^\\(.+\\):"'...

    ,----
    | Checking for library `filladapt'... Found
    | Ispell process killed
    | Starting new Ispell process [default] ...
    | Ispell process killed
    | Local Ispell dictionary set to francais
    | Using the <MyCompany-ID> Identity
    | progn: Search failed: "^\\(.+\\):"
    | Starting new Ispell process [francais] ...
    `----

I have no idea why it is limited to some mails (though I have
the very subjective impression that the problem occurs more and
more), and -- worse -- how to try to debug that problem...

Could you help me?

Thanks a lot in advance,
  Seb

-- 
Sébastien Vauban