You are unable to access the setup page even if everything seems to be setup correctly. You are able to ping the units IP address and you were able to access the user interface from a different computer before.
Please check if the computer has VIPRE Internet Security. This software has an aggressive web filtering feature that can prevent you from accessing the user interface via browser. You can disable Web Filtering and the Firewall feature on the software temporarily to access the EnGenius interface. Simply turn the said features "OFF".