Can you help my mouse?

We use the type that has a digital roller ball, you move the cursor with a ball with your fingers, instead of the whole mouse. Our old one was getting jerky, and sometimes not moving. I thought it might be dirty, but we saw a new one, Kensington Orbit, and it worked fine for two weeks, not it's doing the same thing. Hubby claims he has no problems, but I have trouble moving it over links or boxes, and sometimes it just sits there. Shall I shoot it?