Dapper updates out of sync?

[John Dangler]

I have 2 systems running Dapper, a laptop and a desktop.  I upgraded the
laptop to dapper before the desktop, but it seems that, for the last 3
or 4 updates, the packages for these two systems has been out of sync.
I chalked up the first one or two to the servers being loaded, since I
can use apt-get to obtain the rest of the packages not seen by the
update manager.  But it's still happening.  This morning, I got a notice
on the laptop that 9 packages were available for update.  10 minutes
later, I went to the desktop system, hit the update manager, and got "3
packages" ...  Is the update manager just unreliable?  If so, I'd rather
run sudo apt-get update && sudo apt-get install as a cron job once every
week or so...