How old is the NAD CD player? Are you using 700 MB CD-R (80 minutes) or 650 MB CD-R (72 minutes)?
CD-R are less reflective than pressed discs and older players sometimes have trouble reading them, but if it's only the last few tracks it could be that the player just can't read the 80 minute CD-R. It's also possible that the burned CD is not exactly in spec; ie did not have a 90 second lead-in and 90 second lead-out (did you perhaps use the 'overburn' feature of Nero?). Some players refuse to play those because technically they aren't 'correct'.