It sounds like you have a port forward problem. Go to the support home page http://support.slingbox.com/go/home and make sure you are logged in. See if it shows you any status alerts and that it shows a internet port like 5001.
If any errors re-run the internet setup.
We're having the same problem, after the SlingCatcher working with no problems since Feb. 2010 with no changes to our configuration. We have already tried going through manual setup of our internet viewing and port forwarding on the router. We even tried a new router, and did the setup at least another 3 times. Still, no go.
This happened last year too. Sling Media insisted it was our router, but then when I was back in the country we went through the whole thing with the tech on the phone (after paying the mafia-like fee) and determined my slingbox pro was defective. It was replaced free of charge.
Get a tech on the phone. Stick to your guns until you get a satisfactory outcome.