I found ticket #140 and I have the same error. I didn't modify the database. However, this should probably be logged under a different ticket, but there isn't a create tables script for those of us who don't have permissions to create tables.
I am using:
Linux uawww.domain.com 2.6.18-53.1.4.el5 #1 SMP Fri Nov 30 00:45:16 EST 2007 i686 athlon i386 GNU/Linux
php -v
PHP 5.1.6 (cli) (built: Sep 20 2007 10:16:10)
Copyright (c) 1997-2006 The PHP Group
Zend Engine v2.1.0, Copyright (c) 1998-2006 Zend Technologies
mysql --help
mysql Ver 14.12 Distrib 5.0.22, for redhat-linux-gnu (i686) using readline 5.0
#0 /var/www/html/piwik/plugins/Actions/Actions.php(265): Piwik_DataTable_Row->addColumn('nb_visits', '1')
#1 /var/www/html/piwik/plugins/Actions/Actions.php(111): Piwik_Actions->updateActionsTableWithRowQuery(Object(Zend_Db_Statement_Pdo))
#2 [internal function]: Piwik_Actions->archiveDay(Object(Event_Notification))
#3 /var/www/html/piwik/libs/Event/Dispatcher.php(280): call_user_func_array(Array, Array)
#4 /var/www/html/piwik/libs/Event/Dispatcher.php(250): Event_Dispatcher->postNotification(Object(Event_Notification), true, false)
#5 /var/www/html/piwik/modules/PluginsManager.php(422): Event_Dispatcher->post(Object(Piwik_ArchiveProcessing_Day), 'ArchiveProcessi...', Array, true, false)
#6 /var/www/html/piwik/modules/ArchiveProcessing/Day.php(69): Piwik_PostEvent('ArchiveProcessi...', Object(Piwik_ArchiveProcessing_Day))
#7 /var/www/html/piwik/modules/ArchiveProcessing.php(237): Piwik_ArchiveProcessing_Day->compute()
#8 /var/www/html/piwik/modules/Archive/Single.php(80): Piwik_ArchiveProcessing->loadArchive()
#9 /var/www/html/piwik/modules/Archive/Single.php(117): Piwik_Archive_Single->prepareArchive()
#10 /var/www/html/piwik/modules/Archive/Single.php(306): Piwik_Archive_Single->get('UserSettings_pl...', 'blob')
#11 /var/www/html/piwik/plugins/UserSettings/API.php(108): Piwik_Archive_Single->getDataTable('UserSettings_pl...')
#12 [internal function]: Piwik_UserSettings_API->getPlugin('1', 'day', '2008-03-15')
#13 /var/www/html/piwik/modules/API/Proxy.php(462): call_user_func_array(Array, Array)
#14 [internal function]: Piwik_API_Proxy->call('getPlugin', Array)
#15 [internal function]: Piwik_API_Proxy->getPlugin('1', 'day', '2008-03-15')
#16 /var/www/html/piwik/modules/API/Request.php(140): call_user_func_array(Array, Array)
#17 /var/www/html/piwik/modules/ViewDataTable.php(352): Piwik_API_Request->process()
#18 /var/www/html/piwik/modules/ViewDataTable/Html.php(45): Piwik_ViewDataTable->loadDataTableFromAPI()
#19 /var/www/html/piwik/modules/Controller.php(43): Piwik_ViewDataTable_Html->main()
#20 /var/www/html/piwik/plugins/UserSettings/Controller.php(114): Piwik_Controller->renderView(Object(Piwik_ViewDataTable_Html), true)
#21 /var/www/html/piwik/plugins/UserSettings/Controller.php(11): Piwik_UserSettings_Controller->getPlugin(true)
#22 [internal function]: Piwik_UserSettings_Controller->index()
#23 /var/www/html/piwik/modules/FrontController.php(119): call_user_func_array(Array, Array)
#24 /var/www/html/piwik/index.php(62): Piwik_FrontController->dispatch()
#25 {main}