I upgraded my ubuntu system two weeks ago (AMD64) from 7 to 8.04. After the upgrade (successful) I noticed the update manager seemed to hit an infinite loop while preparing to download automatic updates. After a reboot it worked normally and updated my system. The next time automatic updates were available, update manager seemed to hit the infinite loop again before downloading any updates. I checked the process in system monitor and update manager was sleeping. I rebooted, but the problem has persisted and update manager starts normally but never gets around to downloading updates or updating my system. It has been several days and I now have 70+ updates waiting for download and install but update manager continues to sleep rather than download files and update my system. Most recently I get the error message "Not all updates can be installed" with the option to do a partial upgrade. Clicking on 'partial upgrade' closes the dialog box and nothing else happens. Any thoughts on how to get back to normal automatic updating?