Can't add DHCP Reservation with Airport Utility I just bought an AirPort extreme (bought December '12). I'm trying to assign a static IP for my printer.

With Airport Utility 6.2, under Network, I click on the plus sign under DHCP Reservations. All I get is a beep and it doesn't do anything. 

Router mode is set to DHCP and NAT. 

What is preventing me from adding a DHCP Reservation?
Download Airport Utility 5.6. This older version of Airport Utility will let you make DHCP Reservations. (I had to resort to this because Airport Utility 6.2 ignored the plus sign under DHCP Reservations. It also ignored the Edit button and needed a "Force Quit" to terminate.)