Replying to my own post... I may have a solution...
I re-downloaded the last image segment (.nos) on a lark as the error occurred when the ISO file was almost done being created. I then re-ran the EXE... I now have an error-free ISO image and a DVD in hand.
Seems that uncompressing and concatenating the NOS files doesn't provide much info if there is a problem with them...
Hope this helps a few of you with the same issue.