gnupg fails during packaging

[Mauro Darida <robertnospam@nonsense.com>]

I notice the following error at the end of a package session:
dpkg-deb: building package `debianadv' in 
`../debianadv_0.0.20050516-1_all.deb'.
 signfile debianadv_0.0.20050516-1.dsc
gpg: skipped `Mauro Darida <mauro.darida@istruzione.it>': secret key not 
available
gpg: [stdin]: clearsign failed: secret key not available

but typing
$ gpg --edit-key mauro.darida@istruzione.it
you get:
gpg (GnuPG) 1.2.5; Copyright (C) 2004 Free Software Foundation, Inc.
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions. See the file COPYING for details.

Secret key is available.
              ^^^^^^^^^^^
pub  1024D/28A61681  created: 2003-04-22 expires: never      trust: u/u
sub  1056g/530E09AF  created: 2003-04-22 expires: never
(1). Mauro Darida (none) <mauro.darida@istruzione.it>
(2)  [jpeg image of size 3071]

Anyone to explain this apparently odd behaviour??
-- 
On this laptop no Windows system survives and LINUX POWER reigns UNLIMITED.
Successfully Microsoft free since December 2002.
GnuPG key ID: 28A61681