The AutomaticUpdater is designed to last the lieftime of your application. It should be placed on your main form and last until your app closes (at which time Windows, by design, cleans up all the memory).
That being said, a number of people do what you do (put the AutomaticUpdater on the "login form" or "splash screen" of an app). We're going to make the AutomaticUpdater more flexible for cases like these.
In the meantime just put the AutomaticUpdater on your main form.