Error: Cannot mount ISO image from network folder?

Hello, under Win 8 Pro 64-bit, I discovered the following oddity: When I try to mount an ISO image using the Windows' built-in mounting function, it works when the the ISO is located on a local drive, but NOT if it is on a network drive (linked to my NAS). The latter case yields an error saying that mounting failed without further explanation. (YES, the Iso file type is associated to Windows...