sap script

Hi Experts,

In my requirement When i see print preview of a delivery documnet from VL02N i have one line item in main window.The O/P is perfect.But when i press back button and see the o/p immediately once agian by selecting the same out put type there is on ore line item in the print preview.That means the same line item is displaying twice..

Can any body tell me what may be the problem?

Regards