There is a permissions error that can happen with CS6. Have you checked the permissions for your preferences folder?
I agree with Rick. This sounds an awful lot like a permissions error. Make sure the ENTIRE folder structure is correct and not just the top folder!
tthank you for your help and answers. What I've realized is that the folder and file referred to...didn't exist!!
Then looking in a colleague'sMac, I've copied the folder "\preferences\after effects cs6" in my Mac and it works Perfect.