I've complained repeatedly that K3b supplied via Ubuntu 7.10's repositories can't rip DVDs on Ubuntu 7.10. It worked for me on 7.04 as well as on every version of openSUSE I cared to try it on. I tried everything I could think of to get it to work short of installing Kubuntu, which I will never do. I have an abiding dislike of Kubuntu, stoked in part by its silly insistence that Konqueror is the default web browser, not Firefox.
After repeated attempts to find a solution on forums and via Google, I solved my problem the old fashioned way; I downloaded the source to K3b 1.0.4 and built it myself. And you know what? I can rip DVDs now with K3b on Ubuntu 7.10.