Thank you for using our Answers forum. I have a couple of articles which I hope will help you. The first one is, Some internet security and personal firewall may interfere with your Slingbox setup or Slingplayer. The second article is, What's port forwarding/port mapping? The last article that I have for you pertains strickly to the port forward. It is Help setting up Internet viewing.
Hope this all helps.
Slingmedia Moderation Team