"Default Boot Device Missing or Boot Failed" Error Message
 

Just installed Linux Mint 17.3 Cinnamon on an Acer Aspire E 15. When the computer boots, I'm getting a message "Default Boot Device Missing or Boot Failed". If I hit ENTER it takes me to the Boot Manager. If I hit ENTER again, the Grub Menu for Cinnamon comes up and I can get into Cinnamon although I get 2 error messages while it starts. The first is about ACPI and the second is about BGRT. I have no idea what they apply to. This was a full UEFI install.

Boot Repair log at http://paste2.org/V4ztnA15

Thanks in advance for your assistance.

You have mixed MBR installs with UEFI. You can see at the top of the boot repair output that Grub is in the MBR. It should not be as you are using UEFI and there is a separate EFI partition on sda1 with both windows and Mint efi files. Boot repair might have installed Grub to the MBR, I don't know. If it did, that was a mistake. The link below explains why mixing MBR/EFI doesn't work.

https://help.ubuntu.com/community/UEFI

You might take a look at ubuntuforums as there are quite a few posts there with solutions to the problem. Don't use it myself so...