If you're going to upgrade, I suggest going to the latest version. Or *at least* 1.2.7 if you're not prepared to jump to the 1.3 series which has a much easier templating system and oodles of new features etc.
As to dealing with your current issue, you likely have table prefixes of "zen_" on all your tablenames. As such, change "ALTER TABLE admin_activity_log ..." to "ALTER TABLE zen_admin_activity_log ..."



