PowerBuilder 12.5 Classic GhostScript creating blank pdf

I am using window 7 x32. PowerBuilder 12.5 Classic and GhostScript 9.1w32

I am trying to update an old script (written in PB8) which used to use a Jaguar server to generate PDF documents, but for whatever reason that is no longer supported/working with PB12.5.

I have installed GhostScript 9.1 and the registry HKLM\SOFTWARE\GPL Ghostscript\9.1\GS_DLL points to gsdll32.dll and I have a Sybase DataWindow PS printer available

The PB Code I am using to generate the PDF is:

lstr_pdf_props.s_string[1] = "filename.pdf" 
... 
dw_statement.Object.DataWindow.Export.PDF.Method = Distill! dw_statement.Object.DataWindow.Export.PDF.Distill.CustomPostScript="No" 
dw_statement.SaveAs(lstr_pdf_props.s_string[1], PDF!, false) 

This completes without error and creates a C:\filename.pdf file 3kb in size, however it is a blank page, the file opens in adobe reader but there is no writing or anything printed, just a blank white page.

Does anyone have any ides as to what might be going on here?

thanks.