We have been running CiviCRM 4.6.8 for a while now on our site. Last evening, while trying to access our site, Wordpress gives us this error: The plugin civicrm/civicrm.php has been deactivated due to an error: The plugin does not have a valid header.
we had plans to update to 4.7.9, so we backed up our SQL database and entire CiviCRM installation and proceeded with updating to 4.7.9 as per https://wiki.civicrm.org/confluence/display/CRMDOC/Upgrading+CiviCRM+for+WordPress. However, when point our browser to the upgrade url: http:///wp-admin/admin.php?page=CiviCRM&q=civicrm/upgrade&reset=1, we get this error: You do not have sufficient permissions to access this page.
I would have thought that upgrading would have resolved any issues with invalid headers, but now it seems we have even further issues. Any ideas on how to go about resolving these problems?