It's necessary to check some settings on the router to find out why the Internet Viewing setup is not going through. I recommend to use the Network Setup Assistant to create the rule on the "first" router. Please note that use the term first, that's because it's necessary to check if the modem now has a public or a private IP address, in this last case, it will be necessary to create a rule on the modem but it will be for the router, not the Slingbox. Using the E1000, create the rule for TCP and UDP using the port 5001 or the one you preferred. If you use a different port, remember to change it manually during the Internet Viewing setup using Setup at slingbox.com. On the router's interface, access the tab status to check the Default Gateway IP, if that address starts with 10, 172 or 192; you will have to setup also the modem. Have a look at these links, they will help you with this configuration
If the issue persists, I recommend you, to check with the ISP (Internet Service Provider) if your network has a static IP instead a Dynamic IP.
Hope this helps. Let us know how that works