Error while posting PO

Hello friends,i created a PO whose delivery date is of dec of 2012 and packing slip date is feb i am getting error that period for 11/06/2011 is not posting has been cancelled.all periods are created and open.the date which mentioned in the error that period is closed.but since i mentioned earlier there is no meaning of these date here as creation,delivery date is in 2012 and 2013