Hello It means that the IP address, the number your computer gets given so it can use the Internet, is already in use by another computer on your network.
Possible causes and solutions:
1) You have a router that dishes out IP addresses by DHCP, but you have a device on your network that has an IP address manually assigned. Check that all of your devices are set to have IP addresses automatically assigned.
2) You have two routers that are both dishing out IP addresses and conflicting with one another. Disable DHCP on one of the routers.
As an easy temporary resolution you may find that simply restarting the MacBook will cause it to be issued a new, different address.
Thanks mini, but why would it change all the sudden? We do have a wireless router and everything else works just fine. Could something have just changed on its own? NOTHING is different
Okay, wait, we did just get Direct TV, but I can't imagine that would effect it...I did use the mac the same day we had it installed, but not since we have started downloading On Demand shows.