I believe there was a slingbox system update that took place last week, and believe this may be the reason you were "knocked off" the network. I too am experiencing not being able to connect (living in Europe), and have yet been able to resolve it. I think any configuration settings you previously set need to be reset from your host site (where the sling is actually located). Hopefully if you do this it will be fixed. Mine is in the states so I need someone else to do this for me.
Also, in my experience it is the actual host site's internet speed that is the issue, so again in my case in the states. If the cable/internet provider isn't providing enough speed or others are using that same host network then sling has issues.