Are the beans oily? I get this problem occassionally if I use older or bought beans that have an oily surface. The oil can make them stick and since you dont have the weight of more beans to push them through they can get stuck.
Solution - I dunno. I have read that others have removed the plastic cone in the middle of the hopper to help the beans feed. But this is a finger guard!!! - so be sure first and see what others have to say before removing it. Maybe you need fresher beans.
Best idea is only to use what you need and keep the rest in an air tight bag or tin in a cool place out of the light. A bag is better I find since I can push excess air out.