Just wanted to note that this segfault happens with this patch in place:
And without it (i.e. in Lucid), I don't get the segfault - but of course Thor doesn't play there.
I think it's like peeling an onion. As the top bugs are exposed and fixed, more are revealed. There are more issues in libdvdread that valgrind complained about, but I didn't have time to investigate all of them. I hope to eventually...