Are you using the router in conjunction with a cable or dsl modem?....... If you are it is possible that the modem and the router have the same IP address preventing you from having access to the router configuration settings. If that is the case you will have to change the IP address of the router.

To find out if they have the same IP address: you will have to run a command prompt (cmd) and enter the ipconfig/all command, once with the router hooked up and once with just the modem without the router hooked up. If you see that the gateway is the same IP address: usually something like 192.168.2.1 then you know you are having this issue.