If you have not already, please try resetting your Slingbox to factory settings. This article : How to reset your Slingbox to factory settings walks through the steps.
Let me know if that resolves your issue
I have the exact same issue with 2 brand new, out of the box 500's. I've been waiting for tech support for over 20 mins. Hard reset just leads me back to the config screen again where it does the same thing. I can't get past step 4 of the config process. They both downloaded updates when first set-up and since then they've basically been bricks to me. Very bummed.