Yes, I also have a Dell XPS 1640, if that still doesn't work for you, I don't understand why it is solved for me. Have you tried an apt-get upgrade ? Very strange... Before this was solved this was my temporary solution : https://launchpad.net/~makson96/+archive/fglrx I hope it will help you, but this problem stays with the opensource driver (eventhough I don't know why it's now working for me).
** Attachment added: "Xorg.0.log" https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/1174042/+attachment/3661686/+files/Xorg.0.log -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1174042 Title: System crashes with open-source radeon driver To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/1174042/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs