@alism I' ve checked them all, and my client doesn't have admin level and cannot install plugins. So nothing from the inside.
A Hack maybe. The host (godaddy) has been under attack latelly. I've had some non-wp sites hacked not long ago.
@Shane G I've read the article, and there are some simple issues I will try, but I have to do it in a low trafic schedule cause I need to deal with DNS to get the site up again.
As an alternmative, I've backedup the old DB, created a new one dumped the SQl file in it and run fresh instalation of wp in another directory, pointed DNS and I have a "New" site running.
But since the main plugin on the website (a virtual e-shop), that took me months to adapt, was working under an old wp-version, now with the updated wp version it runs with some errors and my client is a bit annoyed cause Christmas is near...
I kept the original version online, hoping I can find a solution, and be hable to login again.
Sorry for my not-so-good english, but my native language is Portuguese.
Thank you all!