This topic applies on a GN4 server.
The GN4 Everyone group and the apppool user that is running IIS (it may be NETWORK SERVICE in IIS6 & 7) should have a full permissions on the TEMP directory, as specified in the SERVERCONFIG.XML, in order for the COM modules to work.
Please note that in the default SERVERCONFIG.XML, the Temp directory is not specified, thus the default one is used. You may want to set a specific temp directory.
Open the file (typically in C:\tera\GN4\main\config\global) and search for TempDir, then enter a valid path.
Reset IIS and restart GN4.
Note
The upload transfer the file to the client computer to a temp location on the IIS server. If the permissions are insufficient, you will get access denied.