Signing key errors

[NoOp]

[Karmic 32bit 2.6.31-20-generic]

I am getting the following errors today on repository updates (sudo
apt-get update) only on this one system:

W: GPG error: http://download.virtualbox.org karmic Release: The
following signatures were invalid: BADSIG DCF9F87B6DFBCBAE Sun
Microsystems, Inc. (xVM VirtualBox archive signing key)
<info at virtualbox.org>

I've redownloaded the key directly:
http://download.virtualbox.org/virtualbox/debian/sun_vbox.asc
and manually updated:
sudo apt-key add sun_vbox.asc
w/o error.

I've also used the full combined command:
$ wget -q http://download.virtualbox.org/virtualbox/debian/sun_vbox.asc
-O- | sudo apt-key add -
OK
w/o error. Yet I'm still getting the update error.

$ sudo apt-key list
/etc/apt/trusted.gpg
<snip>
pub   1024D/6DFBCBAE 2008-07-14
uid                  Sun Microsystems, Inc. (xVM VirtualBox archive
signing key) <info at virtualbox.org>
sub   2048g/78A86EAF 2008-07-14

Which is correct & what I show on my other systems. Note: I'm getting
same on my bitdefender key as well. It also is correct and working on
the other systems.

Any suggestions as to how I can clear & resolve without having to
remove/reset all my other repository keys as well?