apt-get error

[kbun at xpresso.seaslug.org]

Just a bit ago, I tried to do an apt-get update/upgrade,
and got the following error message:

Ign http://ppa.launchpad.net precise/main Translation-en_US
Ign http://ppa.launchpad.net precise/main Translation-en
Fetched 388 B in 3s (122 B/s)
Reading package lists... Done
W: GPG error: http://ppa.launchpad.net precise Release:
The following signatures couldn't be verified because
the public key is not available:
NO_PUBKEY D258A9281AF466B2

I tried checking the files in /etc/apt, in order to
comment it out and try again, but I couldn't find
a reference to launchpad in any of them. I'm sure I'm
missing something, but what/were is it?

TIA

Bill