verifying a tar.bz2 file fails:

ntinstall:/usr/src# rm -rf /root/.gnupg/

ntinstall:/usr/src# gpg --recv-keys 517D0F0E
gpg: directory `/root/.gnupg' created
gpg: new configuration file `/root/.gnupg/gpg.conf' created
gpg: WARNING: options in `/root/.gnupg/gpg.conf' are not yet active during this run
gpg: keyring `/root/.gnupg/secring.gpg' created
gpg: keyring `/root/.gnupg/pubring.gpg' created
gpg: no keyserver known (use option --keyserver)
gpg: keyserver receive failed: bad URI

ntinstall:/usr/src# gpg --recv-keys 517D0F0E --keyserver pgpkeys.mit.edu
gpg: "--keyserver" not a key ID: skipping
gpg: "pgpkeys.mit.edu" not a key ID: skipping
gpg: requesting key 517D0F0E from hkp server keys.gnupg.net
gpg: /root/.gnupg/trustdb.gpg: trustdb created
gpg: key 517D0F0E: public key "Linux Kernel Archives Verification Key
<ftpadmin@kernel.org>" imported
gpg: no ultimately trusted keys found
gpg: Total number processed: 1
gpg: imported: 1

ntinstall:/usr/src# gpgv gpxe-1.0.0.tar.bz2.sign gpxe-1.0.0.tar.bz2
gpgv: keyblock resource `/root/.gnupg/trustedkeys.gpg': general error
gpgv: Signature made Tue Feb 2 17:32:17 2010 CET using DSA key ID 517D0F0E
gpgv: Can't check signature: public key not found

^^^^^^^^^^^^^^^^^^^^

Public key is well known to gpg!