I don't know if this will help you or not but, I've been reading this thread and it made me think of something that happened to my Dad once. He used to have a Doberman/Southern Coon mix. He was a great dog, big dopey and friendly. And then when he was somewhere between 1 and 2 years old he started getting aggressive for no apparent reason. My Dad took him to the vet and they told him that it had something to do with the growth of his brain and it was causing pressure on his skull. I think they gave him medication but I don't remember. My Dad ended up having him put down because the dog got aggressive with him too.