Read this on a website about night terrors - maybe it will help:
" As Night Terrors usually occur between 15 minutes and an hour after the child falls asleep, gently awaken your child just before you yourself go to bed. Tuck them in and say goodnight. Often, this disturbance of the sleep pattern will prevent them from having an attack that night. This needs to be repeated each night.
Another approach is to note the approximate time that a child has regularly attacks, then gently awaken the child, 15 minutes before he or she usually has the attack, then tuck them back into bed. If the above methods don't help and the attacks are violent, talk to your doctor about possible medication.
If you find that your child is experiencing a Night Terror, the best response is to hug and reassure them. Agree with everything they say or do. Don't shout and tell them they are only dreaming, as this only seems to upset them more and can have an adverse effect."
here