Firstly, running gconftool-2 as sudo is definately wrong. If something's not working right away, don't just put sudo in-front and think it'll magically work.
Secondly, gconftool-2 needs to know how to contact dbus. This is unfortunately cumbersome. The first thing you need to know, is which display the X server is running at. If you have only logged in with one user, the display number is usually 0, so if we assume that:
EDIT: The above is if you ssh in (or similar) to your box. If you are running it locally, the above should not be needed as the needed variables will be inherited; you only need to remove the sudo.
# display number, assuming 0
# get the machine-id
read -r machineid < /var/lib/dbus/machine-id
# source the right file under .dbus to set the needed variables
# export the variables sourced from that file
export DBUS_SESSION_BUS_ADDRESS DBUS_SESSION_BUS_PID DBUS_SESSION_BUS_WINDOWID
# Run gconftool-2
gconftool-2 -s -t bool /desktop/gnome/remote_access/enabled true