I have a mac intel 2.66 running 10.7.5 as my main computer. I have an additional G5 mac in another building running Leopard. I have an apple extreme connected to my cable modem. I have added an additional airport extreme in another building about 60'

I am assuming that the connection between the AirPort Extreme base stations is a wireless one ... correct? I am also assuming that both base stations are 802.11n or later models. If so, then both base stations need to be configured for an extended wireless network. Please use the following Apple Support article for reference.

Ok, thank you for the updates. Both base stations should be configured for a roaming type of extended network. Please refer to the link I provided earlier for the correct setup.

The basic requirements for a roaming network are:

• The base station must be interconnected by Ethernet. (Your's is already.) Note: Connect the Ethernet cable between the LAN port of the first base station and the WAN port on the "extending" base station.
• Each base station must have a unique base station name.
• The "extending" base station must be in bridge mode. (Your's is already.)
• Each base station must use the same wireless network name, security type, and password.

With both base stations in a roaming configuration, each will have its respective Ethernet ports active, and both, will be broadcasting it own Wi-Fi network ... but those wireless networks will have the same name (aka, SSID) so wireless network client can roam between them.