No notification of Natty upgrade

I'm running Kubuntu 10.10 and I haven't gotten the notification of the Natty upgrade. I've tried several alternate ways of getting it, none of which do anything:

1. sudo apt-get update
    sudo apt-get upgrade

2. Synaptic shows no upgrade even after a reload.

3. Neither kpackagekit nor the Ubuntu Upgrade Manager knows anything about the upgrade either.

Here's informationabout my system:

pwa@pwa-K60IJ:~$ uname -a
Linux pwa-K60IJ 2.6.35-29-generic #51-Ubuntu SMP Fri Apr 15 17:12:35 UTC 2011 x86_64 GNU/Linux
pwa@pwa-K60IJ:~$ cat /proc/version
Linux version 2.6.35-29-generic (buildd@allspice) (gcc version 4.4.5 (Ubuntu/Linaro 4.4.4-14ubuntu5) ) #51-Ubuntu SMP Fri Apr 15 17:12:35 UTC
pwa@pwa-K60IJ:~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=10.10
DISTRIB_CODENAME=maverick
DISTRIB_DESCRIPTION="Ubuntu 10.10"

Please confirm that in Update Manager -> Settings... Release Upgrade "Show new distribution releases" is set to "Normal releases".

Almost everyone who's looked at the problem suggests that "show new distribution releases" hould be set to "normal releases", but it's already set to that and has been all along. The unfortunate effects of my struggles now is that after reinstalling kpackagekit, it segfaults on startup!!

I do get notification of updates. I checked that by reverting a package (khelpcenter4) to an earlier version. I then got a notification that it needed to be updated, which is of course the correct effect.

I'm about ready to bypass the problem by downloading the Alternate Distribution CD and installing from there. But there has to be a bug here that will bite others sooner or later.

How can I learn about the mechanism by which distribution upgrades are detected and the notification issued?

This looks like a comprehensive list of upgrading choices. It seems the live CD can do it too since Natty:
http://askubuntu.com/questions/12909/how-do-i-upgrade-to-the-development-release-aka-ubuntu1

As for finding the root cause I have no idea. Sorry.

I had three systems running Kubuntu Maverick: one in a second partition on the same system as the one I was working with, and another on a different machine entirely. And none of the three got the notification or could pick up the upgrade with do-release-upgrade, which leads me to believe that the problem might not be in my systems at all.

I've bypassed the whole problem by using the Alternate CD, and with that everything went smoothly, including retrieval of packages from the Net. The only bump in tne road was the problem with samba4, which I'm sure you know about, since it generated a boatful of duplicate bug reports. It ought to be fixed quickly, if for no other reason than to stop the deluge of bug reports.

I've seen other scattered reports of the same problem.

I keep seeing more reports of this problem as people chime in on the threads I put up about it. I'd suggest that an analysis of do-release-upgrade would provide useful clues as to what's missing.