Let me understand better your issue.
You are trying to install Ubuntu 14.04 on Intel® NUC Kit 5CPYH and it already has the latest BIOS version 0048. Isn’t it?
My troubleshooting is the following, get into the BIOS and reset the settings pressing F9 then, save changes with F10. It is better to use 1 memory stick of DDR3L-1333/1600MHz 1.35V and 2.5” HDD or SSD. Plug 1 monitor to the NUC using VGA or HDMI 1.4b high speed cable.
Turn the NUC on, and keep tapping F10, select the UEFI – USB Ubuntu bootloader or USB Ubuntu bootloader, continue with the OS installation instructions.
Let me know how it goes.