dog acting scared of us all of a sudden

Question
My 18 mo old black lab is acting scared of all of us.  We got her at about a year old and had never done this before.  I had to drag her into the house and then she went in her cage and if one of us tried to talk to her she would not even look at us,she would turn her head away.
I got her to come out about an hour later to go for a ride and now she will come to me but no one else.  Please help my youngest son is so upset because she wont even look at him.
We don't beat her and really do't yell at her much.  

Answer
Labs do not mature until 3yrs or so. There is still time. Not all dogs are tail wagging lick your face off kind of dogs. There is a few things you can try,. Like when she is in her crate, try sitting with your back towards her. Don't face her, pet her and talk with her. Some dogs are crate shy. When they are trapped in a cage and can't escape from someone or something. I have had this happen with customers for many years. The trick is not for the dog to see your expressions. If your don't know the dogs background it is impossible to explain all the behaviors but something has caused the dog not to trust humans. Someone may have accidentally shut a door on her foot. It may be small but to her in means fear. Hope I helped some.