when you say you cannot connect, do you mean you cannot connect to the slingbox while you are away from home? or do you mean you cannot connect to your slingbox at all (either while you are at home or away from home).
if the problem is just while you are away from home, does a simple restart of your router and slingbox solve the problem? if it does, i would think that the problem is with your router.
If the latter problem is what you are experiencing and a simple restart doesn't fix it, the problems is probably with the slingbox.
i couldn't find anything in the slingbox support site that covers this very well. but I believe that if the issue is with just the connecting while outside your home, that the problem is most likely with those port forwarding settings in your router.