Comment 36 for bug 53868

From 9.04 and onwards there has been a change in how the user is notified if there are available updates.

Read http://www.ubuntu.com/getubuntu/releasenotes/1004#Change%20in%20notifications%20of%20available%20updates

To restore how it used to be with the orange icon, run:

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