How can I get Update Manager to Check & Notify for DAILY updates

In Software Sources, I have Update Manager set to check for updates DAILY. I also selected the setting to Notify but not to download or install updates.

Considering my settings, Why do I not receive Daily notifications when updates are available?

For example, Google Chrome PPA released a SECURITY update Tuesday. Yet as I write this my Update Manager has not alerted me that there is an update available for my Google Chrome PPA. From past experience I know that if I manually run Update Manager the Chrome PPA update will be available.

How do I get Update Manager to CHECK and NOTIFY for updates DAILY? I do not want to have to manually run Update Manager on a daily basis to see if there are updates available.

This happens on both Lucid and Natty.

In Startup Applications - Update Notifier is enabled.

Using gconf-editor check that the Auto-Launch checkbox as shown in this image is ticked.

(As found by Nick) - check also that the option (highlighted) "regular_auto_launch_interval" is set to zero.