Comment 27 for bug 326609

please check your upgrade log if you spot something like Jamie posted:
...
Downloading...
--2009-04-18 21:05:57-- http://archive.canonical.com/pool/partner/a/adobe-flash
plugin/adobe-flashplugin_10.0.22.87.orig.tar.gz
Resolving archive.canonical.com... failed: Name or service not known.
wget: unable to resolve host address `archive.canonical.com'
download failed
The Flash plugin is NOT installed.
...

If so, you probably got struck by the network connection disappearing during upgrade. Thats fixed in latest update-manager, so new upgrades wont end up in this situation.

Anyway, if you have this in your dist-upgrade term.log, please attach that log file. Thanks