mactheripper problem

I've just encounted a problem for the first time using this program. I have an internal drive and an external. Basically, I usually switch between dvd's and pick which one I want to extract. Sometimes im watching one, while ripping another. Suddenly, I cant switch to the other dvd. It shows the dvd and changes the name in the little box but doesnt actully change the content. It rips the same dvd. I tried repairing permissions, pram, and reinstalled the program. Any other ideas.