It seems that you are having some issues setting up the Slingbox for Internet Viewing with a Thomson modem.
The main issue is that you need to connect the Slingbox to a router, since this is the only network device capable to create and assign IP addresses. The modem does not have this capability.
We recommend you to check if the modem is also a router. If it is, make sure to include the specific model number. This way, other forum users will provide you with the right steps to follow in order to set it up.