Your EFI system partition is corrupt: you will need to repair it using dosfsck, or preferably, with chkdsk/scandisk in Windows.
** Changed in: grub-installer (Ubuntu) Status: Incomplete => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1495570 Title: Re-installation of Ubuntu 14.04.2 LTS alongside Windows 8.1 failed. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub-installer/+bug/1495570/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs