You appear to have grub2 installed in the MBR of sdb, yet grub legacy is actually installed in the filesystem. Your bios is probably configured to boot the broken grub in sdb firs,t then when you exit, it falls back to sda. Choose which system you want to be in charge of booting. If you want Xubuntu, then boot into it and run sudo dpkg-reconfigure grub- pc and select both drives in the menu, then boot into Kubuntu, and remove the grub package. If you want Kubuntu, then boot into Kubuntu and run sudo apt-get install grub-pc and select both drives in the menu, then boot into Xubuntu and run apt-get remove grub-pc.
** Changed in: grub2 (Ubuntu) Status: Confirmed => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1018419 Title: grub fails to boot OS images on second hard drive To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1018419/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs