I understand that you need some assistance in order to set up your Slingbox PRO HD with both of your routers.
We can offer you a couple of options in order to fix this issue. First, check the following third-party links and follow the included steps in order to set up your Slingbox PRO HD for Internet Viewing.
If you are not able to set up the Slingbox with any of these routers, I recommend you to check this link if you want to connect both of your routers on the same network.
Help setting up Internet Viewing when you have multiple routers