Wordpress login Error 404

Hey guys,
Today I tried to login to the admin part of my WP and no luck - the instalation redirected me to 404 error. And this happens to all blogs installed on the same hosting. Can someone give me an advice how to fix this. Already tried deleting/editing .htaccess, changing cmods, deactivating themes/plugins. Yesterday it was working, today not. And I haven't made any changes

i believe it's happening because of the hosting needs to add your IP to let you access to admin panel...can you access the ftp?

If you can FTP in:

Check your chmod settings -
http://www.techzoomin.com/wordpress-login-issueswp-admin-showing-404-error-page/

If you can't, get in touch with support at your hosting company.

Mindseye.