Hi Carl,
I had exactly the same problem with my D54250WYK, I found my problem was my optical mouse. It appears that the NUC bios looks for an optical device when it reboots following the initial file load of W7 from the DVD drive, and when it found the mouse it looked for suitable drivers, which obviously didn't exist - don't forget the bios is only as clever as the person who writes the program.
Anyway, my cure was simple; when W7 reboots following the initial file load, pull out the mouse USB plug until the NUC has found the correct DVD drive and started loading files again, then simply plug the mouse back in and it works just fine.
Hope this helps someone else.
Cheers, ... John