Comment 9 for bug 175166

I believe one can get the old functionality back by doing this (as mentioned in the release candidate, release notes)

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Change in notifications of available updates

Ubuntu 9.04 introduces a change to the handling of package updates, launching update-manager directly instead of displaying a notification icon in the GNOME panel. Users will still be notified of security updates on a daily basis, but for updates that are not security-related, users will only be prompted once a week.

Users who wish to continue receiving update notifications in the previous manner can restore the earlier behavior using the following command:

gconftool -s --type bool /apps/update-notifier/auto_launch false

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