Yeah, my Aussie has a simular problem. She'll go get the ball, grab it, but she won't come back. She just wants to play keep a way and tag, haha. Maybe you can try teaching her to fetch with a leash. You'll need two people. Have one person throw the ball, and have the other person leash your dog. When your dog chases the ball, the person with the leash will follow. When she is close to the ball, put it in her mouth and then walk her back to the person who through the ball with your leash. I did a bad job explaining, but...try it. I don't know if it'll work, but I'm just guessing...