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:
[02/08/12 3:07:36] [ ERROR: ][ No content found with content_id = 14328]