Not sure, but this might help you. I think that you may have to rotate your model before slicing, as a quick read is that it slices in the x, z plane.

In AutoCAD, make sure your trees are "blocks". You should be able to edit one tree in ACAD and see all others change at once. Then, when you import to SketchUp, those blocks become components. If you double-click on a SketchUp component you can add something inside and that object will appear in all instances of the same component. This is what he did.

What happens if you turn on View/Hidden Geometry, and then Zoom extents? I think if the edges have been hidden, you could get this result when using a sketchy line style.

Hallelujah! Thank you solo

UPDATE: Ive just bought a ASUS Nvidea EN9400GT (1Gb RAM), was cheap (UK £40), installed and working, has corrected my "selection" problem and is now super fast.... I was on an Intel Board which that inbuilt unit was 512Mb RAM (so wasnt a slow unit) however seems to be all about the OpenGL componant of the graphics board. Many Thanks @donaldaugustsson said: ok, i have ATI Radeon graphiccard and it have been alot of problem with that card... what card do you recommend, cause i am tired of a the problem