I'm sorry to hear of your trouble trying to access your Slingbox on the local network. Are you using Watch on Slingbox.com? Honestly, that isn't a usual error message indicating what is wrong from Slingbox.com. It sounds like you may be using older SlingProjector software that is no longer supported and was designed for use with the SlingCatcher.
Could you please verify if you are using a supported operating system and browser to view your Slingbox on Slingbox.com?
Hope this helps, please reply back with additional information if necessary!
The Sling Moderation Team