As explained in the forum post:
http://forum.piwik.org/read.php?2,94533,94575#msg-94575

I am trying to do the following:

• report "Starting pages" (Aktionen->Eingangsseiten in the german interface)
• interval any (1 day, 1 week, 1 month, ...)
• at the end of the list choose "show flat"
• then apply a filter (inserting a keyword in the textbox at the end of the list)

The error I see is (if I manually open the url in the browser):

The DataTable object has not yet been created

Stacktrace:
0 /path/to/piwik/plugins/Actions/Controller.php(386): Piwik_ViewDataTable->getDataTable()
1 /path/to/piwik/plugins/Actions/Controller.php(332): Piwik_Actions_Controller->configureGenericViewActions(Object(Piwik_ViewDataTable_HtmlTable))
2 /path/to/piwik/plugins/Actions/Controller.php(81): Piwik_Actions_Controller->configureViewActions(Object(Piwik_ViewDataTable_HtmlTable))
3 function: Piwik_Actions_Controller->getEntryPageUrls()
4 /path/to/piwik/core/FrontController.php(138): call_user_func_array(Array, Array)
5 /path/to/piwik/index.php(53): Piwik_FrontController->dispatch()
6 {main}

Example URL on demo.piwik.org:
http://demo.piwik.org/index.php?filter_column=label&filter_column_recursive=label&filter_sort_order=desc&filter_offset=0&keep_summary_row=0&module=Actions&action=getEntryPageUrls&idSite=7&period=year&date=2012-10-03&enable_sort=1&filter_sort_column=entry_nb_visits&filter_limit=100&search_recursive=1&viewDataTable=table&controllerActionCalledWhenRequestSubTable=getEntryPageUrlsSubDataTable&totalRows=17&enable_filter_excludelowpop=0&flat=1&filter_pattern_recursive=list.php

Opening a ticket as requested by Matt.

P.S. I am pretty sure it was working in release 1.8.3
Keywords: API export flatten