OS restarts EVERYTHING constantly!!!! WHY!!!

Every now and then, probably every two to three weeks, when I restart my computer for something, it will come onto the desktop with everything gone. Nothing will be erased, all my documents and files will still all be there, but my dock is back to the default settings, all the data in my itunes library is gone, my mail accounts are gone, all the settings like the arrangement of folders is gone and every customizable setting on my whole computer is back to default. Why is this happening. Is there a reason or do I just have to reinstall Mac OS. I'm running the current version of OS with an intel imac 20inch core duo. Help Please!!!!

It sounds like your Library folder in your home directory is being erased. I'm not sure what would cause that short of file system corruption, though?

Have you changed your home directory name?

what do you mean by that. Do you thing filevault has anything to do with it.