An error occurred while trying to write to the log: failed to open stream: Permission denied.
Check that the log file (/var/www/vhosts/portokalada.com/httpdocs/log/pa.log) is writeable by the web server.
Here's the message I was trying to log:
[05/20/12 23:39:32] [ ERROR: ][ Throwing exception DB_QUERY_FAILED | Message: DB Error: unknown error | SQL that caused this exception: SELECT * FROM user_profile_data WHERE 1 AND field_name = ? AND user_id = ?]