I just started it up in online mode, and was fast enough to be able to switch the setting to not update automatically before it started downloading. I think you can also pause a download before it finishes, so if you aren't quick enough to change the setting, you might be able to do that too.
On a related note, why can't you change the setting while in offline mode? That's just strange.
On a related note, why can't you change the setting while in offline mode? That's just strange.