TypeError: oSettings is null

anytime i try to add data using fnAddData i get the TypeError: oSettings is null the line the error is thrown on is oSettings.aoData.splice( 0, oSettings.aoData.length ); in the jquery.datatables.js . here is the code - the oSetting error is thrown in the _fnClearTable so i dont even get to pass the data in

medListTable.tblMedList.fnClearTable();
medListTable.tblMedList.fnAddData(medListTable.data); //the data part of your json message
medListTable.tblMedList.fnDraw();