VS 2010 RC and SilverLight Client Proxy with collections

I have this application. Some of the data types in server application are collections of type ObservableCollection.

Example:
public class VisitCounts : ObservableCollection[visitcount]
{
}

In VS 2008 silverlight client application generates a proxy where I can still reference ObservableCollection in e.Result (of async calls).

For whatever reason, VS 2010 RC is not able to generate proxy with these special collection types (even after tweaking the advanced options).