I went through the entire process of preparing the nLite files, complete with intregrating drivers and all and got to the final point (where I found out I needed cdimage.exe, which I copied into the nLite folder, and then restarted nLite and did it all again) and EACH TIME it goes right through the process of creating the ISO file but right at the end of that process dies and tells me that the ISO was not written. What's the problem?

my nlite does not have that file.

and it made the iso file

nLite uses mkisofs.exe to create the ISO.

Make sure you press the "Make ISO" in the page and then "Next".