My ActiveX can't write a file to a local folder

I've written an ActiveX control that transfer a file using FTP commands and then writes the file to a local folder on the client PC.
All is working fine when under VS2008 but when invoking the ActiveX from the production server I've got a problem in writing the downloaded file to the local folder.
Of course, I've given this folder the permission to write  to the IUSR account but this not solve the problem.
Any other ideas?
Thanks,
Marco
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