I'm trying to create a dataview webpart using SOAP service connection as a data source. When I'm passing authentication information directly using second option i.e. "Save this username and password in the data connection" then web-part is working and fine and displaying data.
 
But when I'm trying to use SSO as authentication mode then SharePoint Designer is not able to add DataView webpart using that connection and displaying error in Data Source Detail pane "The server returned a non-specific error ....".
 
When I checked ULS log then I found this error:
"System.UnauthorizedAccessException: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED)), StackTrace:    at Microsoft.SharePoint.SPWeb.InitWeb()     at Microsoft.SharePoint.SPList.get_IsUserInformationList()     at Microsoft.SharePoint.Utilities.SPListItemChangesHelper.ExecuteQuery(Boolean bUseDefaultViewQueryWhenEmpty, String strRootFolder, String strListName, String strViewName, String strQuery, String strViewFields, String strRowLimit, String strSince, String strQueryOptions, String strContains, SPWeb web, SPQueryOpt queryOpts, Hashtable updates)........".

But user configured in SSO is a Site Collection Administrator.

Does anyone know how to use SSO in SOAP data source connection? Any help is appreciated.