I was lucky and didn't have this problem with any of my kids (Dominic is only 3 so there's still time, but the other 3 we didn't have this problem).
However, I know that this particular thing works for my kids as it worked for me when I was a child. Now don't laugh, this is going to sound very silly, but the simplicity of it is quite amazing. Again, I don't know if it will work, but it's worth a shot!
Most dreams comes from the subconcious, or so I've been told. This of course is what is in the back of your mind. When I was little, if I watched a scary movie, or thought of something scary, before I would lay my head on the pillow I was say to myself, out loud, "I'm not going to have any bad dreams tonight, only good ones".
I'm not sure why it always worked, but it did. And it works for my kids too. Now again, mine haven't experienced night terrors (nightly nightmares) so I don't know if this would work for you, but I think that me being in control of my dreams when I was a child helped me to conquer my fear of them. By telling myself I wasn't going to dream anything bad, I became in control of the situation.
Hope I didn't ramble too much
