"invalid passphrase"

[John Aldrich]

Per Ingo Klocker, I have disabled caching of the passwords for signing of 
emails. I have built everything and configured my KMail as set out in the 
"how-to" page at http://kmail.kde.org/kmail-pgpmime-howto.html.
I have run the test described there and it works, verifying that my passphrase 
is valid.
HOWEVER, I still get "invalid passphrase" when I attempt to sign an email 
using the built-in KMail GPG support. I *also* get an error *WITH NO 
OPPORTUNITY TO ENTER A PASSPHRASE* when I use the plugin.
I'm using RedHat 9.0 and KMail 1.5 (KDE3.1-11).
I've tried everything I know to try, and just about everything that has been 
suggested. I have specified my default key in .gnupg/gpg.conf, and I still 
get no prompt to enter a password when using the plugin and an "invalid 
password" option when trying to sign using the built-in GPG support.
Any ideas?