If I save a registration (frontend and backend) then the system asks me in a popup to choose the "title". I haven't added any customized fields and I have reinstalled CB. When this popup appears, the form in the back is gone and after accepting the popup-message (clicking OK), it will be reloaded. Any hints?

I wish I could delete this message I found the problem. My users component was modified with additional fields. I think, that's the reason why this problem happen. I hope I can use CB instead adding the fields to the original users components.