192.168.x.x is a series of reserved private addresses that are not routed on the Internet usually used for private networks, that are then routed out to the internet by some for of router that has a real (public) internet address on the front of it. If you're machine is reporting that the address is not available, then it's talking about your router most likely, for some reason it cannot reach it. check your ethernet cable connections, even unplug and replug them in at both ends, sometimes the contacts oxidize and break the connection. where the cable plugs in to both the computer and the router, there should be a little green light that comes on when the connection is good (it's called a link integrety light), make sure you see this on both sides.