The old Emulab interface (which we affectionately refer to as Emulab Classic) has been deprecated for a while, we are no longer doing any active development on it. If possible, you should consider switching over to the new Portal interface which is complete redesign of the web interface and experiment workflow model.
The most important feature of the new Portal interface, is that NS is no longer used as the specification language for experiments. Instead, we now use Python to describe experiments. Lots of information and a tutorial can be found in the new Emulab Documentation.