It is not a good thing for women to do office jobs. They will have to face non-related (non-mahram) men even though they are wearing a veil. She will have to have interaction with them which is where fitnah (evil and mischiefs) begin. A father is committed to provide maintenance to his daughter and a husband is asked to provide maintenance to his wife. So, there is no need for women to do jobs which always pose harms [sic] and mischief.
[A later rulling dated November of 2008 by the same institution regarding the permissibility of women working in offices took a different position: "It is permissible for women to work in an office provided they observe the full hijab and fulfill the requirements set by sharia." See question header: 'Can women work in an office?']