What do these warning messages mean

[Jerry]

I periodically run the following commands on a FreeBSD-8.2 amd64
machine:

/usr/local/bin/gpg2 --keyserver wwwkeys.us.pgp.net --refresh-keys

/usr/local/bin/gpg2 --edit-key clean minimize save

These commands produce output that has several of the following
messages displayed:

gpg: subpacket of type 20 has critical bit set

gpg: key 60AE908C: removed multiple subkey binding
gpg: key 60AE908C: invalid subkey binding

The number of such messages varies according to the signature. The
majority of signatures have no warnings whatsoever. Then, I
occasionally see this message (name intentionally obscured)

gpg: key 36E54C93: invalid self-signature on user ID "User Name <user at domain.com"

I don't know what these messages mean and if there is something I am
doing incorrectly.

Thanks!

-- 
Jerry ♔

Disclaimer: off-list followups get on-list replies or get ignored.
Please do not ignore the Reply-To header.
__________________________________________________________________