"Account determination for entry 1000 AUM not possible".

Dear all.

i have a stock in unrestricted. whn i am trying to transfer between unrestricted to salres order stock(412 E) system showing error "Account determination for entry 1000 AUM not possible". But next time i m spliting the material and transfering that time system wont throws any error. say example i have to transfer 40 materials from unrestricted to salesorder stock, upto 39 system wont throws any error. if i put full qty system throw the error "Account determination for entry 1000 AUM not possible". This AUm is we areusing for sto only. pls tel me how to rectify this error.