I did a bit of reading on Friday after the 3.6 update and a lot of people who encountered problems with previous updates followed these steps and were successful.
This is presuming you have access to the back end of the website via FTP/ CPanel:
– Open up the wp-config file within the public html folder.
– add the following lines near the bottom of the page:
define(‘SCRIPT_DEBUG’, true);
define(‘CONCATENATE_SCRIPTS’, false);
just before the line that reads: require_once(ABSPATH . ‘wp-settings.php’)