Hi,
I asked you to create new user account. Have you tried this?

Have you tried this solution:
http://upandready.typepad.com/up_and_ready/2012/09/autocad-lt-alert-the-directory-may-be-locked-by-a...

Plus there is another topic about such issue :

https://forums.autodesk.com/t5/autocad-for-mac-general/can-t-open-autocad-2012-on-my-macbook-pro/td-...

Maxim