To add to Michael's post, I am experiencing the same problem.
About 3 days ago I lost the ability to connect to my slingbox. I tried rebooting and resetting but to no avail.
When everything is connected the power light and the SlingBox HorseShoe light are permanently on but the network light is out. I have tried alternative ethernet cables but no difference.
I'm thinking that because of the illuminated lights that the power source is probably not the issue and that it is more likely that the ethernet port orsomething on the circuitry specific to that port has failed.
If anybody has any advice or tips on how to fix or at least confirm what the source of the issue might be I would be very grateful.
Lots of other folks have reported similar connectivity issues that were traced to a failing power supply. There may be enough volts and amps getting through to light the lights, but not drive all of the other electronics reliably. Those who have tried a replacement power supply are typically reporting -- if they report back at all -- that their problem was solved, at least temporarily. I suspect that the SB is drawing a rather significant amperage -- with possible spikes -- out of that 5 volt power supply and thereby causing periodic problems. Getting a 4 ampere supply as noted in the prior post may well be a long-term solution.