Start by resetting the AEBS. The reset button is on the back.
Then see if you can't start over. After you reset it disconnect the power from the AEBS, modem, and computer. Wait at least one minute. Turn on the modem and wait for the status lights to show communication with your ISP. Then turn on the AEBS and wait until the status light turns green (or solid orange after blinking orange.) Then turn on the computer. Open Airport Utility to check that you are now connected and to determine what additional configuration you need to do such as setting up your WPA2 security passwword.