Problem with theming form for my module setting page
It's because you haven't defined a theme registry entry called form_style, but you're setting the form's theme handler to a function with that name.

You just need to change your implementation of hook_theme() to match the function name and form theme setting you've actually defined:

function actionadscatalog_theme() {
  $path = drupal_get_path('module', 'actionadscatalog') . '/templates/admin';
  return array(
    'form_style' =&gt; array(
      'render element' =&gt; 'form',
      'template' =&gt; 'actionadscatalog-admin_run_import',
      'path' =&gt; $path,
    ),
  );        
}