another thought here...personal story:

My twin boys went to kindergarten in Alabama. They had wonderful, loving, warm teachers who hugged a lot. During one Christmas break a substitute teacher was brought in, a German lady who spoke with a strong German accent. She was warm and loving, but the accent upset one of the boys so much he started stuttering. (The other boy was in love with her.)

I don't know a lot about child development, but it seems that at that age they are very susceptible to change. I had to spend almost a year of nonverbal play before all traces of stuttering left.