Fatal Errors Using Autodesk Civil 3D 2006

[eph67]

I am running Civil Design in Autodesk LDD 2006 and receive Fatal Error: Unhandled Access Violation Reading 0x000 Exception at xxxxxxxxx. The errors seem to occur when I invoke commands that require heavy computational work like grading to a surface, building a surface, or generating contour lines. I am using a P4 chip at 2.8ghz w/ 1gb RAM.

Has anyone had similar problems and what was the solution?