do-release-upgrade finds no new release from Oneiric

I'm running Kubuntu 11.10 and I cannot upgrade to v12. "do-release-upgrade" says "no new release found" no matter what I do. I've updated everything in sight, including the repository list, with both Synaptic and Muon. Also "apt-get update", "apt-get upgrade", and "apt-get dist-upgrade". I've tried specifying both "Long term releases only" and "any new release" in Synaptic's update settings. No errors or indication that there's anything left to update or upgrade.

I know that many others have gotten the correct notification, but at least one other person has encountered the same problem I have.

More info:

pwa@pwa-K60IJ:~$ apt-cache policy update-manager-core
update-manager-core:
  Installed: 1:0.152.25.12
  Candidate: 1:0.152.25.12
  Version table:
 *** 1:0.152.25.12 0
        500 http://security.ubuntu.com/ubuntu/ oneiric-security/main amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu/ oneiric-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1:0.152.25 0
        500 http://us.archive.ubuntu.com/ubuntu/ oneiric/main amd64 Packages