I had the same experience on my computer with a 4850. For some reason xorg.conf isn't being updated to the new virtual screen size. If that setting is written elsewhere, then it's not being used.
** Changed in: gnome-control-center (Ubuntu) Status: New => Confirmed -- gnome-display-properties does not edit xorg.conf virtual desktop correctly in karmic for dual head https://bugs.launchpad.net/bugs/438715 You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gnome-control-center in ubuntu. -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs