I am getting a 500 Internal Server Error when trying to access my System Status screen (the warning in footer is "System Status: Error"). I get a 500 error when I try to access some of the Search functions as well: (Find Contacts / Advanced Search etc).
Wordpress 4.7.5, CiviCRM 4.7.19.
I had Debugging/Backtrace turned on, and ran into this:
#0 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/Error.php(187): CRM_Core_Error::backtrace()
#1 [internal function](): CRM_Core_Error::handle(Object(DB_Error))
#2 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/PEAR.php(921): call_user_func((Array:2), Object(DB_Error))
#3 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/DB.php(985): PEAR_Error->__construct("DB Error: no such field", -19, 16, (Array:2), "SELECT civicrm_custom_field.id as civicrm_custom_field_id, civicrm_custom_fie...")
#4 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/PEAR.php(575): DB_Error->__construct(-19, 16, (Array:2), "SELECT civicrm_custom_field.id as civicrm_custom_field_id, civicrm_custom_fie...")
#5 [internal function](): PEAR->_raiseError(Object(DB_mysqli), NULL, -19, NULL, NULL, "SELECT civicrm_custom_field.id as civicrm_custom_field_id, civicrm_custom_fie...", "DB_Error", TRUE)
#6 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/PEAR.php(224): call_user_func_array((Array:2), (Array:8))
#7 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/common.php(1905): PEAR->__call("raiseError", (Array:7))
#8 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/common.php(1905): PEAR->raiseError(NULL, -19, NULL, NULL, "SELECT civicrm_custom_field.id as civicrm_custom_field_id, civicrm_custom_fie...", "DB_Error", TRUE)
#9 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/mysqli.php(933): DB_common->raiseError(-19, NULL, NULL, NULL, "1054 ** Unknown column 'civicrm_custom_group.is_public' in 'field list'")
#10 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/mysqli.php(403): DB_mysqli->mysqliRaiseError()
#11 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/common.php(1216): DB_mysqli->simpleQuery("SELECT civicrm_custom_field.id as civicrm_custom_field_id, civicrm_custom_fie...")
#12 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/DataObject.php(2446): DB_common->query("SELECT civicrm_custom_field.id as civicrm_custom_field_id, civicrm_custom_fie...")
#13 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/packages/DB/DataObject.php(1635): DB_DataObject->_query("SELECT civicrm_custom_field.id as civicrm_custom_field_id, civicrm_custom_fie...")
#14 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/DAO.php(357): DB_DataObject->query("SELECT civicrm_custom_field.id as civicrm_custom_field_id, civicrm_custom_fie...")
#15 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/DAO.php(1307): CRM_Core_DAO->query("SELECT civicrm_custom_field.id as civicrm_custom_field_id, civicrm_custom_fie...", TRUE)
#16 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/BAO/CustomGroup.php(537): CRM_Core_DAO::executeQuery("SELECT civicrm_custom_field.id as civicrm_custom_field_id, civicrm_custom_fie...", (Array:0))
#17 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/Page/View/Summary.php(64): CRM_Core_BAO_CustomGroup::getTree("Individual", Object(CRM_Contact_Page_View_Summary), "2", NULL, "")
#18 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/CRM/Contact/Page/View/Summary.php(87): CRM_Contact_Page_View_Summary->preProcess()
#19 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/Invoke.php(310): CRM_Contact_Page_View_Summary->run((Array:3), NULL)
#20 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/Invoke.php(84): CRM_Core_Invoke::runItem((Array:14))
#21 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm/CRM/Core/Invoke.php(52): CRM_Core_Invoke::_invoke((Array:3))
#22 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-content/plugins/civicrm/civicrm.php(1227): CRM_Core_Invoke::invoke((Array:3))
#23 [internal function](): CiviCRM_For_WordPress->invoke("")
#24 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-includes/class-wp-hook.php(298): call_user_func_array((Array:2), (Array:1))
#25 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-includes/class-wp-hook.php(323): WP_Hook->apply_filters("", (Array:1))
#26 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-includes/plugin.php(453): WP_Hook->do_action((Array:1))
#27 /home/59460-47919.cloudwaysapps.com/nzgxzrukdb/public_html/wp-admin/admin.php(222): do_action("toplevel_page_CiviCRM")
#28 {main}