it's me again, sorry all my questions. I've ran into an error message coming up every time I edit an user. The line of code which causes the error is the following one:
SPUtility.Redirect("FBA/Management/UsersDisp.aspx", SPRedirectFlags.RelativeToLayoutsPage, HttpContext.Current);
The url seems to be correct, at least the folder FBA in 14/_layouts exists and the usersdisp.aspx file is there aswell. After editing an user, I'm redirected to the overview page immediately. Nothing serious here.