I got it.
Thousends of error messages! Mainly mkdir during the update and actual
#1 DEBUG: SQL ERROR: Query failed with message 'Unknown column 'last_error_date' in 'field list'' - SELECT `id`, `user_id`, `name`, `email`, `email_addr`, `password`, `server`, `smtp_server`, `is_imap`, `incoming_ssl`, `incoming_ssl_port`, `smtp_port`, `smtp_use_auth`, `smtp_username`, `smtp_password`, `del_from_server`, `outgoing_transport_type`, `last_checked`, `is_default`, `signature`, `workspace`, `sender_name`, `last_error_date`, `last_error_msg`, `sync_addr`, `sync_server`, `sync_pass`, `sync_ssl`, `sync_ssl_port`, `sync_folder` FROM `og_mail_accounts` WHERE `id` = '1'
#2 FATAL: exception 'DBQueryError' with message 'Query failed with message 'Unknown column 'last_error_date' in 'field list''' in ...feng_sky/environment/library/database/adapters/AbstractDBAdapter.class.php:386