Hi Palli,
Sorry for the re-posting.
In fact the issue was fixed once I grant write access right at the web server for the authenticated users on the .NET temp file folder:
C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\XXX
where XXX is the website name
I think the only improvement required is the returning of an informative error message rather than simply returning Files.Count = 0.
Thanks.