A.A.
Could be night terrors, but I think it's more sleep deprivation. Your child, I believe, is too young to have given up naps. They all fight it at certain ages, but if you stick to your guns, they'll take the naps.
I noticed that my 5 year old is growing out of her naps...but if she has a melt-down or wakes up crying/screaming, I know the next day is a nap day. So far, she's taking 1-2 naps a week. Sometimes more, sometimes less.
Believe it or not, the more sleep your child gets, the better they sleep.
I would strongly advise getting the book "Healthy Sleep Habits, Happy Child" by Marc Weissbluth. I don't agree with the CIO method he prefers, but it does tell you about the vicious cycle of not enough sleep in children (and B.). I noticed it in my own daughter. Even when she would fight her naps, I would just let her know that it was 'rest time' and that she didn't have to go to sleep, but she did have to play quietly in her bed. 9 times out of 10, she would fall asleep within 10-15 minutes of going up to her room. Even now, when she doesn't need a nap, she's just naturally taking 'rest time' after lunch. She grabs a book, lays on the couch and reads for about an hour. It really helps to get my son (10 months) quieted down to fall asleep for his own nap.
By the way, here is a website to offer a bit more information on sleeping/sleep habits: http://www.med.umich.edu/1libr/yourchild/sleep.htm