This bug just ate my LVM2 volume group. Thanks for nothing. What a stupidly named set of options. Whoever wrote that code needs to be shot. Thank christ I took a backup of the most important data (including my kids first words) or I'd be really buggered now. Also of note: "Undo changes to partition tables" does NOT restore the disks to their previous unmolested states. This is NOT intuitive OR sane behaviour.