B.C.
It sounds like sleepwalking.
It's pretty common in kids and most out grow it by the time they are teens.
http://kidshealth.org/parent/general/sleep/sleepwalking.html
Additional:
You sure can talk in your sleep!
I'm a sleep talker.
When I was in school in chorus my Mom would hear me sing in my sleep.
To this day my husband occasionally has conversations with me in the night that I have no memory of in the morning.