Take a look at this article, especially if your Slingbox does not respond to the reset button (as in the lights on the front not changing at all):
Hope this helps!
Our Pro-HD box also lost network connection within the past few weeks. I have tried resetting the box but nothing. The power light is okay but the network light is dim, sometimes static, sometimes flickering. I have tested the router, the cable and everything is working fine. If I unplug the Slingbox and then reconnect the power lead, the power light comes on immediately, the lights at the front of the box flash for a split second and then nothing. I have always had a dodgy power cable connector but no amount of wiggling does any good.
Is there something else I can do to try and get the box to work or is it now time to consign it to the local IT scrapyard?