System Status page empty and status remains 'critical' after updating from 4.7.8 to 4.7.11 on Drupal 6
For some the answer has been to resolve the Timezone error, if it is present - see: http://civicrm.stackexchange.com/questions/14841/error-datetimezone-construct-unknown-or-bad-timezone-7200

If you have stumbled upon this thread more recently - we found a blank status page after a recent upgrade from 4.6.30 to 4.7.27 where there was no timezone error, in fact, no errors at all in the logs. The solution was to change "Asset caching" from "Auto" to "Disable" (/civicrm/admin/setting/debug?reset=1).