[Techtalk] Repository/GPG issues

[Amanda Babcock Furrow]

Last night I installed EasyPeasy 1.5, which is an Ubuntu Jaunty 
distribution.  It ran one series of upgrades almost fine (there
was one error message in amongst that; anybody know where I could
find a log of errors?)  While it was installing all the initial
patches and upgrades, I also restored my home directory including
some of the dotfiles (but not .gnome2* or anything that looked 
like it would interfere with upgrades!)

After both of those operations were finished, apt-get and the
update manager are now broken, or at least their connections to 
two of the repositories.  The update manager error message is: 

W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://us.archive.ubuntu.com jaunty Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster at ubuntu.com>

W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used.GPG error: http://ppa.launchpad.net jaunty Release: The following signatures were invalid: BADSIG 3B22AB97AF1CDFA9 Launchpad PPA for Ubuntu-X

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/jaunty/Release  

W: Failed to fetch http://ppa.launchpad.net/ubuntu-x-swat/x-updates/ubuntu/dists/jaunty/Release  

W: Some index files failed to download, they have been ignored, or old ones used instead.

The error I'm getting from apt-get is "E: Package <foo> has no installation candidate".

How do I troubleshoot the GPG key problem?  I suspect that may
be at the root of things.

Thanks,
Amanda