I've already encountered this error and this is the best solution I've found:
In your root folder (probably called public_html)please add this code to your .htaccess file...
REPLACE the 00.00.00.000 with YOUR IP address. If you don't know your IP address buzz over to What Is My IP - The IP Address Experts Since 1999
#By Marky WP Root Directory to deny entry for WP-Login & xmlrpc
<Files wp-login.php>
order deny,allow
deny from all
allow from 00.00.00.000
</Files>
<Files xmlrpc.php>
order deny,allow
deny from all
allow from 00.00.00.000
</Files>
In your wp-admin folder please add this code to your .htaccess file...
#By Marky WP Admin Folder to deny entry for entire admin folder
order deny,allow
deny from all
allow from 00.00.00.000
<Files index.php>
order deny,allow
deny from all
allow from 00.00.00.000
</Files>