CrossRoads:
Nick Gammon's sketch doesn't want to compile on Arduino IDE 1.0.1.
Did you put all the files into the same folder, Atmega_Board_Programmer?
I did and then opened Atmega_Board_Programmer.ino, compiled just fine.
I have used the Atmega Board Programmer and it is nice, and it appears to install the 1284p well enough, but again, uploading a sketch ~25kB fails with the paged_write error. Blink uploads fine. I have also tried pulling the hex out of another hex file and putting in, same problem.
The Atmega328 works flawlessly. The 25kB sketch uploads perfectly.