I am having the same issue. I just installed smart slider, and had some permissions issues in the /wp-content/cache folder that I resolved, and then I got this.
Uncaught ReferenceError: njQuery is not defined admin.php?page=nextend-smart-slider2&controller=sliders&view=sliders_slider&action=dashboard&slider…:295
Uncaught ReferenceError: njQuery is not defined admin.php?page=nextend-smart-slider2&controller=sliders&view=sliders_slider&action=dashboard&slider…:425
