I've got AutoCAD 2006 and I'm working with some pretty large 3D models. After adding more and more complexity to it, AutoCAD keeps crashing more and more frequently. The file size is a little under 100 MB and I've got 2GB of RAM on my 5.66MHz dual processor machine. These are some of the typical problems I'm getting:

-error message saying "FATAL ERROR"
-error message saying "Not enough memory"
-AutoCAD just freezes
-Rendering just stops half way through processing

If AutoCAD has to shut down, it usually gives me the option of attempting to save a recovery file before exiting (which doesn't work - it crashes when I load it). Sometimes, it also lets me write up an error report to send to Autodesk.

My best chances of rendering my model are just after rebooting my computer, starting AutoCAD, loading the file, and saying render right away (especially if I have shadowing off and other options that take up more time) - but it seems like the more steps I take (rotating, zooming, playing with layers, etc.) the more likely it is to crash when doing something heavy like rendering or saving.

To me, these symptoms seem like a problem with too little memory. But I've got 2GB! Isn't that enough?! The AutoCAD specs for 2006 say I should be able to get away with 1GB. The file itself is only 100MB - how could it take up more RAM than HD space? Is it possible that there are some memory leaks in AutoCAD? This would make sense out of how it crashes more often after doing several steps.