Created Unassigned: Error using updated library in Win 8.1 [357]

I have updated the Caliburn.Micro, Caliburn.Micro.Extensions, Callisto and Windows.UI.Interactivity dll's in my windows store 8.1 project ( Dev machine is windows 8.1 pro ) , and I have pulled them in from the

Caliburn.Micro v1.5.2 Snapshot\bin\WinRT\ directory.

My app is giving me this error still with the updated DLL's imported.

Error 1 Cannot find type System.Collections.CollectionBase in module mscorlib.dll.

Any ideas what might be causing this?


I am referencing the EventAggregator objects.