I have a Silverlight app that is using the MVVM pattern. I have a WCF service which will allow me to authenticate users (I don't have direct control over that service - assume it is a black box that just returns me the user info and a list of privileges the user has). So, when the app starts up, I want to pull security data from that service.

Right now, when I do this, my views and view models can end up getting initialized before the service returns with the security data. This causes problems because the view models need to disable buttons and make things visible/invisible based on the user having certain privileges.

Is there a pattern that allows me to prevent the initialization of the views / view models until the WCF call has returned? How would you go about solving this problem as elegantly as possible?