Verifying/fixing a failed (?) upgrade to 13.04

[Adam Funk]

Yesterday I upgraded a machine from 12.10 to 13.04 using the GUI from
the update-manager.  Something mysteriously died towards the end (I
got some /var/crash/_whatever) & I can't figure out how to tell if the
upgrade worked or not.  When I log into the machine it shows this:


Welcome to Ubuntu 13.04 (GNU/Linux 3.8.0-19-generic i686)
...
  Graph this data and manage this system at https://landscape.canonical.com/

New release '13.04' available.
Run 'do-release-upgrade' to upgrade to it.


But do-release upgrade does nothing:


/home/adam $ sudo do-release-upgrade 
[sudo] password for adam: 
Checking for a new Ubuntu release
No new release found


and aptitude update && aptitude safe-upgrade do nothing either.  I've
checked that all the entries in /etc/apt/sources.list and
sources.d/*.list have "raring".

How do I verify that my system is upgraded?
If it is, how do I fix the "New release" message?

Thanks,
Adam