If you use a static ip, set your computer to Manual, not Manual with DHCP.
Choose an IP address on the same subnet as your router but outside the range used by the router's DHCP server.
You also have to enter the IP addresses of your primary and secondary Domain Name Servers (DNS) on separate lines in the Domain Name Server box in your TCP/IP prefs panel. (You can probably get that information from the status page of your router's setup utility.