There is a well known limitation with PageMethods that they must exist in the Page not the UserControl. Since the Module is a UserControl dynamically loaded into a page that does not have the method, you cannot use page method there. You would instead have to use a web service.
http://stackoverflow.com/questions/1114957/hot-to-user-autocompleteextender-in-a-usercontrol-ascx-and-place-the-serviceme
Hope it helps,
Joe