That indeed looks like bad disk order. Mathieu, would you be open to trying to disconnect the other drives, leaving just the "right" one in place and seeing if grub is happy then? I would expect you'd only need to disconnect power to the other drives.
Following the same train of thought, is it possible additional drives where added after xubuntu was installed? We should be able to either generate a new device map to account for the unexpected behavior, or get rid of an old stale one. ** Changed in: grub2 (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1316068 Title: error: disk 'hd0,msdos5' not found To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1316068/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs