I´ve been trying to fix this now for two days and it seems as being new with blender I´m totally lost. I have this scene with green screen where five snakes(made out of cubes) are slithering through the view done with simple curve modifier. The snakes are visible in rendered view, but when I render a picture it only shows a supergrainy green screen and no snakes, that should be in the middle of the picture. There´s only one camera and its activated, the right layer is selected and the snakes are not hidden (the camera icon and eye icon are selected). Thanks for any help!
A mesh, hidden in the work view but visible in the render, was in front of the camera. Stupid mistake, but the problem is solved. :J