When the password protect is checked in the screensaver dialog box and the screen saver engages, after typing in your password to reopen, autoCAD Civil3D 2012 gets an fatal error every time. If you try and restart, it just stays in the sartup dialog and runs forever. you do a cntrl-alt-del and it goes into autocad, but none of the commands work. You must reboot again to restart the computer and start all over.

Stop using a screensaver.  It is so old school.  If you don't want anyone seeing what is on your screen either turn the monitor off or do a Ctrl-Alt-Del and lock your computer.

Thank you for your input. I just got a fatal error attempting to do that. I have restarted Civil3D and it is stuck..once again in the start up box showing the message in the lower left corner "Preparing working environment....LAYER" and it will stay there forever if I let it. Cntrl-Alt-del 2 or 3 times will reboot the machine. I will restart and lock the computer and see if I can re-access the open drawing.

Maybe your install went awry.  You could try doing a REPAIR and see if that fixes the problem.