All that I might add to what Tony says is to try using the reset button which is recessed on the back of the unit. Insert the end of a straightened paperclip in the opening and hold it down for longer than the 4 seconds that the manual calls for. What I have seen called for something like 20 seconds.
Here is a Knowledge Base article which addresses network drives not being seen on the network-
At this point, Tony is on top of things and I will step back so as not to muddy the water.
