First, thank you for the help. I later had the same idea with the base class. Know there is some problem with the database. But that's an other problem.
So thanks for your help!
Actually I'm not sure which DataGrid I'm using. I'm quite sure it's not MX, Because I can't find any MX-Code. The DataGrid gets created with a function in its own class. (EntityDataGrid.as)
I do not get any error. The other objects just don't get viewed. (There is an exception rule)