Strange,
having installed countless D-Link routers ,at least 10 on dway, I've seen the same ip problem before. but just unplugging the d-way from the wan(internet)
port, closing the browser, rebooting the router, waiting 5 minutes and opening the config in a browser has always worked.
May i suggest 2 more ideas?
first, use the reset to default procedure, find how in the manual(on the cd)
if that does not work, plug a patch cable from the wan to another LAN port.
the latter is a crazy thing to try as any attempt to contact anything on the internet causes a loop in the routing and may lock up the router. use with caution.