Editing a post: different interface in 2 wp blogs

I have a very strange thing: I have 2 wp 2.1 beta2 blogs on the same server. When I click on edit this (post) in one of them, I have 2 tabs: “Visual” and “Code”, in the other I don’t have these tabs, I just see a “code” page. I have deleted the second blog, copied the first to the second, changed my config.php but the problem (?) remains. So the only thing that is different is the mysql part, I did not touch that of course. Someone an idea?