Hello freddo .
If you still have the 'error' Duplicate entry 'currentTheme' for key 'PRIMARY' it means you have not empty database. Please make sure that you remove all tables from database. Also did your do any changes at /install/installer/configs/installer.ini?
Please, provide us your error.log (or whatever php error log) file contents.
If you are running the Apache web server, add this to the .htaccess file in toaster root
php_flag log_errors On
php_flag ignore_repeated_errors On
php_value error_log /path/to/your/erro/log/file