Sometimes I have the problem that I put some objects in the world (with right-click, new..., and drag into the world) and if I want to "save the world" (with right-click on the world) they disappear from the world, although they were "registred" in the MyWorld-class. If I close Greenfoot and restart, it works fine.
Did anyone encounter this problem? Does anyone have a solution (which is not to restart Greenfoot)?

