Orica attached rights

Can someone help me. I purchased 1,000 Orica shares a few days before it went ex-div (to get the dividend). Anyway, I then noticed on my portfolio list that there was 1,000 Orica shares and 125 Orica rights. I looked them up and it is a right to purchase Orica shares at $15.00. Now that it has gone ex-div I want to sell them so I put the order through as normal to sell the Orica shares and it went through OK, but when I put the order in to sell the 125 Orica rights, I got a warning "Before you proceed, you must be able to deliver title". So I didn't proceed because I don't understand. Why wouldn't I be able to deliver title. They were given to me with the shares. Does anyone know?