While localizing my custom website hosting a Silverlight 3 control, I added multiple resource files (.resx) to my xap and when I hit the page I got this error:
System.Windows.Markup.XamlParseException occurred Message="AG_E_PARSER_UNKNOWN_TYPE
On hitting this link http://www.telerik.com/community/forums/silverlight/navigation/navigation-samples-failing-with-silverlight-3-because-of-urimapping.aspx I realized the goof up. One of the resx files had the constructor still declared as ‘internal’, and you get this error when the application is getting initialized and trying to access and internal resource. So I made the changes to set it to public, and it worked like a charm!!