Thanks for your post.
I have only just got the RC1 up and running.
I am also using win7 but it shouldn't matter, maybe

Use the default settings and join the domain. I am not sure but I think there might be some forrest / domain confusion.
I have managed to join the domain but can't seem to use any M$ admin tools which with samba4 I should.
Still waiting for a reply on this one.
So the default settings with the built in user administrator and password Zentyal 1234.
If you post copy the logs from /var/log/ the zentyal log and module log are prob the most important.
Zip em and attach to the post.
Some of the Zentyal guru's will get back to you in time.
Stuart