Sorry i meant 12.000

Looks like the polycount is the problem then?
DoF needs an additional view for the depth wich should double the triangles, while shade-c may also create some more extra views for reflections and other things, so that might also add additional polygons.
How do you remove grass that is further away? Are you using gamestudios LOD system or something else? Because with those additional views it is possible that some settings aren´t correctly copied from the camera or something.
Some screenshot with debug panel open would probably also help.

But the polycount raises from 113k up to +-1130k ? I would post some shots, but iam not at home, and my internet connection at home is broken. damn ^^
ill take some shots for friday.

I remove/place the grass with gamestudios LOD (CLIP1...) the models are set to STATIC after creation ( like descriped in the manual for seed maps ).

Edit: First of all (this night) ill remove everything (like hdr pp) except grass and the terrain. Then ill test again. But iam pretty sure it will be the same.

sounds like a lot of views to me...