Hi Paul, I also had this problem on a 15 min video segment, and I had 178 gb of space on a NTFS raid drive free. I have a feeling it is caused by a buggy info in the save file. I found in my case by nesting the sequence I was trying to export to dvd inside a new sequence, it encoded fine. Hope this work around helps.
Also to save you time I tried cutting and pasting all the info from the sequence that wouldnt encode to a new sequence, but this didnt fix the problem. Also tried trimming the project and this likewise was not helpful.
So only thing that worked for me was the nesting trick.
kind regards
Cosmic