Fedora 15 won't do automatic updates

[James Bridge]

Using Fedora 15 with Gnome 3 I can only get updates manually, either
with Yum or Software Update. That works fine but it is supposed to check
for updates automatically and it doesn't. The options are set using
"Software Updates" (note the final s!) and I have it set to check daily,
for all updates. Nothing happens. Why not?
-- 
James Bridge <james at xmas.demon.co.uk>