Yes, reserve an ip address in your router for the slingbox, based on the MAC address of the slingbox. Thats what I do with my pro and catchers.
Then the router will always give the same ip address to the device.
I give them an ip address that is outside the normal auto DHCP range set in the router. For example, if the auto DHCP range set in the router is 192.168.1.100.. to .. 200, then set the fixed addresses to 192.168.1. 10.... to... 99, or 201.. to... 250.
When the slingbox powers up and connects to the router, the router will always give it the same address.
Many devices (including some slingboxes) can be manually set to an ip address (within the device), but if another device has already been issued this address by the router, then is a problem. So is better to pre-allocate the address in your router. Hope that makes sense.