client denied by server error

[AlessioD]

I use debian ded. server with plesk 9.5 and I have a problem with apache2 configuration, all error log of mysites return this error:

[Tue May 14 09:55:35 2013] [error] [client XXX.XXX.XX.XX] client denied by server configuration: /var/www/vhosts/domainname/httpdocs/uri-path

I edited /var/www/vhosts/domainname/conf/httpd.include and added these rows:

Order allow,deny
Allow from all

in <Directory> directive but not solved the problem

note: I use varnish cache

thank you