IP Address Reservation

[mspeed05]

I have a WPN824 v2 router and I am trying to do an IP address reservation. I am on the LAN IP Setup page, and I am attempting to add a device under the Address Reservation. I first click Add which displays a list of all currently connected devices and their respective IP and MAC addresses. When I enter an IP address, MAC address and name for a device that is not already on the list I get a Failure message that states "IP Address should be in range [192.168.1.2 , 192.168.1.254]." The IP address I am entering is in that range (192.168.1.20). If I select one of the devices in the list of ones that are already assigned, even if I make no changes to the IP, MAC or name and just click Add, I get the same message. Anyone have any ideas on what is happening, or better yet how to prevent it?