Tenae -
Clean re-installs per Support Doc TS1077667? In your earlier post, you indicate that it only crashes on project files? Are you refering to drawings with C3d objects or Land Desktop project data? Are those project files created with an earlier version of C3d? Have you "recoved" them and any dependent Xref's? Can you log in as someone else on that machine? Administrator or a different user? What profile are you using?
Can you use ProcMon.exe from Microsoft to watch what Civil3d is doing during an open of a drawing that crashes?
Matthew Anderson, PE
Joseph A Schudt @ Associates
Matthew Anderson, PE CFM
Product Manager
Autodesk (Innovyze)