Eh, if the user needs access to it, they must be able to get at it.

I don't think its really possible to do what you want, at least not easily.

Bad port? another bad cable? if its homemade was it terminated properly?

Check your cables, its sound like theyve died or had a short.

I really suggest not using hubs and rather getting routers or level 3 switches (mini routers)

Hubs need to be connected via Cross over cable. not via whatever you usualy buy at bestbuy.