I upgraded a test site before disabling addons and got this error: Admin area: "Mysqli prepare error: Unknown column 'template_map.template_final' in 'field list'" Forum area: "The requested forum could not be found." Then I added "$config['enableListeners'] = false" to the config file. The error disappeared and I could access the forum. Then I tried to disable the addons and got this error: "Please enter a valid callback method (ModEss_Install_105::install)." and could not disable some of the addons. May be I should have disabled all addons first .