I am running Umbraco in Webmatrix on localhost.
I installed Universal Media Picker, all good.
I locally installed the Facebook Provider 1.2, all good.
I created datatype, selecting UnversalMediaPicker, clicked save & settings appeared, all good.
Selected Facebook Provider from dropdown and pressed 'Click to authenticate'.
Popup appears, with facebook login window. Typed my username and passsword and logged in....
... I then get:

Server Error in '/' Application.
The resource cannot be found.
Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable.  Please review the following URL and make sure that it is spelled correctly. 
Requested URL: /umbraco/plugins/theoutfield/universalmediapicker/universalmediapickeroauth.aspx
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.225

Anyone get the same? Not sure what the problem is. Thought it was a folder permissions issue but its not. Any help much appreciated. Thanks.