Mmmm. I dunno. I use the Memorex DVD-R discs as I always do and they worked perfectly for a great deal of time there. If I get this problem again I'll try a "higher quality" brand but I don't think Memorex is that low-quality. Anyway, I made the setting changes suggested by J. Allen
above and no dice.
So I just simply "saved the files to disc" using W.Explorer. It's a rough, unglamorous and clunky way to do it but it works.