pdf generation itextsharp "cannot access a closed file"

Hi,
I managed to generate a pdf taking some data (address of client aso) from database. this works fine and I can generate the pdf without problem but as soon as I try to add some more data from database using a new sql query with a while loop I get the error
cannot access a closed file where the using part of the writer ends. I guess I run out of buffer memory, right?
How can I get rid of that error?
am programming in VB net.

Using FS As New FileStream(WorkingFile, FileMode.Create, FileAccess.Write, FileShare.None) margin = FormatNumber(Utilities.MillimetersToPoints(10), 0) margin2 = FormatNumber(Utilities.MillimetersToPoints(5), 0) Using Doc As New Document(PageSize.A4, margin, margin, margin2, margin) 'PDF start Dim NormalFont As Font = FontFactory.GetFont("Arial", 9, Font.NORMAL) Normal ...