Thanks for your answer.
I think the "generalize" box was checked when i run sysprep.
I didn't get a error message. I couldn't add domain members/groups to the local admin group of a new win server 2008 r2, which i joined to a exist domain.
The AD of the domain is also created by the template. after i re-run sysprep and re-joined the domain, it worked.
I will have a look to the template and will run sysprep again to be sure the "generalize" box is checked.