CS6 Error Message When Burning a Blu Ray Project to DVD

Hi,

I'm trying to burn a Blu Ray project to DVD and I'm getting this message when I try to build the project:

The project is an excerpt from a larger one and contains only 2 video files and no menus. However it's particularly worrying because the project from which this is an excerpt is large and complex. I have created it as a Blu Ray project but my final deliverable is DVD. I really don't want to have to rebuild as a DVD project because it took half a day to link up all of the menus and chapters.

Is there something I need to do in my encode settings?

Thanks in advance.