Use the plateau to take a long, hard look at your exercise routine and your nutrition.
Are you skipping workouts? Make sure you're getting you're doing your workout's as planned.
Have the workouts become easier for you to do? Increase the intensity, by increasing the speed or resistance on cardio machine so that you are working harder.
Are you sticking to your eating plan? A couple of extra "treats" a week may be enough to stop fat loss.
None of the above?
Try changing things up - try a new machine or exercise class. Increase the weight when weight training, or add another set.
Most of all be patient, and don't get discouraged