Hi I have exactly the same problem, can watch slingbox true my Mac, iPhone and iPad with no problem in the same network, so I really think there is something broken in the SlingCatcher. The support have NO solution for me at all. Do I have to by a new Catcher, the one I have is only a year and half.
It seems that you are having some issues with the connection to your Slingbox using the SlingCatcher connection.
As the first step, I recommend you to check if the Slingbox is working fine for Internet Viewing. This will allow you to determine the root cause for this issue. If the Slingbox is not working, you'll need to check and adjusts some settings on your router.
If the Slingbox works fine, you'll need to check some settings at the SlingCatcher network.