do you mean, a NAS connected to a router/switch and accessed by mini it works. but not when you try to access the same storage with an other computer, also connected to that same (wireless router/switch)?
or did you connect the NAS directly to the mini?
I don't know a lot about using a NAS so I don't know if this will work. You might try to add the NAS to the list of items/folders being shared by the Mini.
What are the other machines you are using to connect to the NAS? Are they connecting via ethernet or wifi?