For two months in a row our AP Aged Payables report does not tie out to Accounts Payable on the Trial Balance.  We have never had this problem until two months ago.  The discrepancy amount is not fixed between the two months - we were off by a different amount last month versus this month.  Additionally, when we run both reports as of today they are off by again another amount.  If it makes a difference the Accounts Payable account on the Trial Balance shows a greater balance in the account than the Aged Payables Report.  

Any idea what could cause this? 

Thank you.