Incompatibility with nodewords module

I'm getting the following error when viewing the node for a custom content type which includes a date field. This is happening on all of my custom content types which have 1 or more date fields. If there is more than one date field, I get the same error printed out for each instance of the date field - 5 date fields = 5 copies of this error:

warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, 'theme_date_display_combination' was given in /home/tom/public_html/drupal-6.x/public/includes/theme.inc on line 597.

I'm using the very latest code from cvs.
php 5
core 6.3

I thought that perhaps my existing date fields got corrupt, so as a test, created a new content type, with just one date field, but I still get the error. An export of this newly created content type is below:

$content[type] = array ( 'name' => 'Test', 'type' => 'test', 'description' => 'test for date problem', 'title_label' => 'Title', 'body_label' => 'Body', 'min_word_count' => '0', 'help' => '', 'node_options' => array ( 'status' => true, 'promote' => true, 'sticky' => false, 'revision' => false, ), 'upload' => '1', 'nodewords' => 1, 'old_type' => 'test', 'orig_type' => '', 'module' => 'node', 'custom' => '1', 'modified' => '1', 'locked' => '0', 'image_attach' => '0', 'image_attach_size_teaser' => 'thumbnail', 'image_attach_weight_teaser' => '0', 'image_attach_size_body' => 'thumbnail', 'image_attach_weight_body' => '0', 'print_display' => 1, 'print_display_comment' => 0, 'print_pdf_display' => 1, 'print_pdf_display_comment' => 0, 'xmlsitemap_node_type_priority' => '0.5', 'xmlsitemap_old_priority' => '0.5', ); $content[fields] = array ( 0 => array ( 'label' => 'Testdate', 'field_name' => 'field_testdate', 'type' => 'date', 'widget_type' => 'date_popup', 'change' => 'Change basic information', 'weight' => '', 'default_value' => 'blank', 'default_value_code' => '', 'default_value2' => 'same', 'default_value_code2' => '', 'input_format' => 'd/m/Y H:i:s', 'input_format_custom' => '', 'year_range' => '-3:+3', 'increment' => '1', 'advanced' => array ( 'label_position' => 'above', 'text_parts' => array ( 'year' => 0, 'month' => 0, 'day' => 0, 'hour' => 0, 'minute' => 0, 'second' => 0, ), ), 'label_position' => 'above', 'text_parts' => array ( ), 'description' => '', 'group' => false, 'required' => '0', 'multiple' => '0', 'repeat' => 0, 'todate' => '', 'granularity' => array ( 'year' => 'year', 'month' => 'month', 'day' => 'day', 'hour' => 'hour', 'minute' => 'minute', ), 'output_format_date' => 'd/m/Y - H:i', 'output_format_custom' => '', 'output_format_date_long' => 'l, F j, Y - H:i', 'output_format_custom_long' => '', 'output_format_date_medium' => 'D, d/m/Y - H:i', 'output_format_custom_medium' => '', 'output_format_date_short' => 'd/m/Y - H:i', 'output_format_custom_short' => '', 'tz_handling' => 'none', 'timezone_db' => 'UTC', 'module' => 'date', 'widget_module' => 'date', 'columns' => array ( 'value' => array ( 'type' => 'varchar', 'length' => 20, 'not null' => false, 'sortable' => true, ), 'value2' => array ( 'type' => 'varchar', 'length' => 20, 'not null' => false, 'sortable' => true, ), ), 'display_settings' => array ( 'label' => array ( 'format' => 'above', ), 'teaser' => array ( 'format' => 'default', ), 'full' => array ( 'format' => 'default', ), 4 => array ( 'format' => 'default', ), 2 => array ( 'format' => 'default', ), 3 => array ( 'format' => 'default', ), ), ), );