What I would suggest is to download ethereal or some other free network analyzer and see what, if anything, is going on on the network between your NAS and other devices / internet.
A hub comes in very handy here - especially if you can't set up a switchport as a monitoring port. just use a x-over cable to connect the hub to the switch, then attach the NAS and the PC you are running your sniffer on to the hub. Now you will see all traffic between the NAS and everything else.
SD