Because this is the second time you have gotten infected with the same code, and you have already changed your password, I would suspect that this hacker has got another means of infecting your site. Is this a shared hosting account? Do you have any other sites on this server? It is possible that this hacker is using a vulnerability on another site to infect your DB directly.
It looks as though koumbit.net has disabled you site for now. I suspect they are aware of your infection and have probably contacted you about clearing it up. If you can get them to re-enable the site I can help you clean it up again and see if I can figure out how this hack is getting in.