Can you elaborate on "I created a new mysql database yesterday"?
It sounds like your settings file is not correctly identifying the new database. This could be for several reasons, such as incorrect server address, incorrect username, incorrect password, your new db may not have been given permissions for access by the user you specify (mysql permissions are specified by location), and there could be even more options.
In that case I would guess that your mysql user might have been modified by either adding a password or removing its permissions to your existing eZ database.
Can you see the site if you log in as your ez Admin? Try going to /user/login on your site and logging in. If you see the site then, I would suggest checking your Anonymous role in eZ and make sure it has access to the correct siteaccess.
Debug output would tell you if it is a database access problem or a permissions problem.
Here some tips how to solve the kernel 50 error: http://ez.no/community/forum/install_configuration/migrated_to_new_site_no_content_or_database_contact/re_migrated_to_new_site_no_content_or_databa
Empty the folders var/cache and var/<name of siteaccess>/cache using your ftp access.
Be careful not to delete any other folders!! Please note that reloading the page after that can take very long as eZ has to recreate everything.