advanced rendering for AutoCAD
Send a copy of the model using this upload link and I'll take a look at it. Likely you're running out of address space on your 32 bit system, but I won't be able to tell for sure until I see it here.
I did take a look at this. Once again the culprit is the model units. What you've got here is a model drawn in millimeters, yet AutoCAD and nXt think the units are inches. That makes the model off by a factor of 25.4. Normally the units do not affect the memory usage-- but because you were using trees they had to be scaled way up and were requiring large amounts of memory. I did the following:
This is actually a small, manageable, drawing once you take all of these steps.