What is causing Mint 18.1 "grub-efi-amd64-signed failed to install into /target/" and following installation failure?

The SSD is set to ACHI (whatever it is, it was automatically set). Secure boot is set to Other OS (only other choice). ***Linux only. No Windows. Hate Windows. No dual boot. Microsoft hasn't touched my computer in years. Windows can suck it.*** I formatted both SSD and HDD drives to GPT. - Corsair 30GB SSD (putting / and swap on here) - Old, ~300GB HDD. No problems with the drive have been found. (putting /home here) The live Mint USB isn't corrupt. I did the checksum before installing, and have done multiple checks on the USB before booting. Installing Mint in UEFI mode is resulting in "**grub-efi-amd64-signed failed to install into /target/**". Any forum I found on this error has not had a solution compatible with my problem. That package doesn't appear to exist. The installer ***will fail*** upon this message occurring. I have an internet connection. It's hardwired... (insert Metallica reference here). I can cruise the interwebs during the live boot. Installing Mint in legacy, *not* UEFI, is resulting in no OS being found. **Specs:** - 18.1 Cinnamon (3.2.6) 64-bit - AMD FX-8350 8 core x4 - 8GB RAM - AMD/ATI Turks XT, Radeon HD 6670/7670 I am not sure what the *hell* is going on anymore.