GetSaveFileName API call does not work with Sharepoint documentlib

[MartinLong]

I want to save objects (e.g. outlook msg) to an STS shared document library.

I am using GetSaveFileName(OpenFile) with the OPENFILENAME structure to give
me a "Save as..." dialog. When I navigate to Network places->STS site
name->document library name, the content of the dialog box goes blank.

This function works quite happily if I select "Save as..." from the Outlook
file menu.

Any help or explanation would be much appreciated

Martin