Nero & iso burning

I am sure I have done this before with the same file. When I try to burn a video iso file to DVD as 'Burn image' it comes up with cannot burn to this media, please insert CD. I have selected to use DVD but behind my DVD burner in the box it has (cd/cd/rw) when it should be DVD/DVD/rw.
It will let me burn the iso to DVD as a data file. Am I doing something wrong. I am using Nero reloade 6.
Casey