Latest version of FireGPG installed... Same behaviour...

#4 Exactly!

And my feeling and experience have always been that Mutt and gpg are 100% compatible...

A Linux box, using just one version of gpg installed as /usr/bin/gpg...

I just downloaded FireGPG and I am giving it a try. It would be great for me to have full GPG availability using Gmail!

Then I create a first message, sign it using my key and send it to a test account. I move to Gmail sent mail, open the message just sent, and it tells the signature is valid. However I download the message to the other account, open Mutt, view the message, run the check-traditional-pgp function, and then mutt tells the signature is invalid. If I copy the body of the message shown by mutt and pass it to gpg --verify on the same machine, the signature is agreed as valid. So Mutt, who always worked lovely with gpg, now seems failing.

Any ideas?