come ti dicevo ieri bisogna impostare il MIME

La soluzione come dice macromedia

On the Windows 2003 server, open the Internet Information Services Manager.
Expand the Local Computer Server.
Right-click the local computer server and select Properties.
Select the MIME Types tab.
Click the New... button and enter the following information:
Associated Extension box: .FLV
MIME Type box: flv-application/octet-stream
Click Ok.
Restart the World Wide Web Publishing service.