Just go my NUC today. Added 2x4GB (8GB) G.Skill F3-1600C11D-8GSL. Added formatted OCZ Vertex 4 2.5" SSD. Converted a Windows 7 Home Premium to a USB bootable drive. No matter what, when the NUC boots all I get is BOOTMGR Missing CTRL+ALT+DEL. No matter how fast or how much I press F2, F7, or F10 nothing happens....HELP!!
Are you sure you've made the USB drive bootable?
Seeing this message, the NUC does not have anything to boot from; did you try booting any other PC from the USB drive you made bootable?