It took a while but finally Google Earth processed and accepted my Kickelhahn tower model. The 3d model was created in Blender, later I exported it as .obj for a import in Sketchup.
Blendswap 3d-Model-Download: http://www.blendswap.com/blends/view/61274
Sketchfab 3d-Model browser preview: https://sketchfab.com/show/weyeuTkdMADFF53EZq4U38mmx3P
Trimble 3D-galerie: http://sketchup.google.com/3dwarehouse/details?mid=d23ce214e8d6c3688279567aa9f64362
