WordPress windows phone error

System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
at System.String.Substring(Int32 startIndex, Int32 length)
at WordPress.Model.XmlRemoteProcedureCall`1.cleanAndParseServerResponse(String responseContent)
at WordPress.Model.XmlRemoteProcedureCall`1.OnBeginGetResponseCompleted(IAsyncResult result)
at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClassa.<InvokeGetResponseCallback>b__8(Object state2)
at System.Threading.ThreadPool.WorkItem.WaitCallback_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadPool.WorkItem.doWork(Object o)
at System.Threading.Timer.ring()