Over the next few days, many of you will see these on apt-get updates
W: GPG error: ftp://ftp.us.debian.org sid Release: The following signatures were invalid: BADSIG AED4B06F473041FA Debian Archive Automatic Signing Key (6.0/squeeze) <ftpmaster@debian.org>
These are normal during the transitions from Testing to Stable unfreezing...
There is a whole lot shakin in the debian repo world right now, just be patient and they all will resolve themselves