Thank you so much posila! You are right.

I don't know why the problem has happened but it was matter of authority.
Right answer for me was no.3 - linked page.
The error massage is little different with linked page because it was written in korean and i translated it with similar word.

Anyway I ...

About three days ago, When I launch the game, a steam massage pop up - "Can not start the game(unknown error)" - in korean. I can not find similar things in the FAQ or other posts. It just not work suddenly with unknown error and there are no information for this error... Because of this, I removed ...