Tonight will mark two weeks since National Australia Bank's payments processing flap began, on November 24.The last update, on NAB's website last night, used the same language it has used for days: "We know that some customers are still experiencing inconsistencies and we're actively working to address these as soon as possible."According to a report in the Sydney Morning Herald, the bank faces demands from the Reserve Bank and the Australian Prudential Regulation Authority to explain the stuff-up.The central bank and the banking regulator are concerned about the impact of NAB's system failure on the smooth operation of the country's payment system.