Comment 20 for bug 650525

extras.ubuntu.com seems to have changed key since this bug was first posted, and it no longer matches the one in ubuntu-extras-keyring (2010.09.27). I imported it manually using gpg --recv with the number given in the apt-get update error message. Now when I run apt-key list this key shows up as "Launchpad Application Review Board PPA".

Instructions for importing the key manually are given here:
http://www.ubuntugeek.com/fix-for-gpg-error-httpextras-ubuntu-com-maverick-release.html