I confirm this on edgy. It unmounts all partitions which are not in use, even those mounted from /etc/fstab.
In my case it happens to hda5 (ext3) and hda9 (vfat). Neither root (hda7) nor home (hda8) is umounted - luckily :) I attach /etc/fstab ** Attachment added: "fstab" http://librarian.launchpad.net/6283848/fstab -- on kde logout all disk partition are umounted https://launchpad.net/bugs/78477 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs