Do you have a firewall or router in the middle between your OOL modem and your desktop? If so you need to do port forwarding to allow access from the outside or to do port mirroring. Only ports i know OOL openly blocks is 445 and 25.
Yes the linksys is my firewall and as I said I did the port fowarding to port 21 and works fine. The minute I change the port number on the router and the nas is stops