It is a common problem with an almost limitless range of causes and solutions, but here are several actions that might do the trick.Make sure your router is configured for Dynamic Host Configuration Protocol (DHCP). If it is, so try disabling and re-enabling the DHCP functions. If that doesn't work, disable wireless security and see if you get a connection; sometimes a mismatched Wired Equivalent Privacy (WEP) key can drop the IP address. You should also check for electrical interference from competing devices such as cordless phones, baby monitors, alarm systems, and microwave ovens. Disable all suspect devices, then recheck your Wi-Fi connection. If all else fails, reboot the router and all computers on your network.