Update-notifier problem

[zer0halo]

Update-notifier doesn't seem to check for updates automatically, even
though I have it set to do so under Preferences in Update Manager.

It's only when I manually run Synaptic or apt-get update, that all of
a sudden the update-notifier icon appears in my notification area.
Shouldn't update-notifier check for updates automatically? Is there
something that I should be doing to enable that? Ie, do I have to
manually change something so that update-notifier runs as a daemon in
the background and checks for updates? Or do possible updates only
appear when a manual apt-get update (or Synaptic) is run?

-- 
"Impossible is nothing."