ok, solved on my own... the CSS file will be not included into the block if it is shown at a "non catalog page" for example the "terms and conditions" . You have to include the CSS like this

function theme_uc_catalog_special_products(){
drupal_add_css(drupal_get_path('module', 'uc_catalog') .'/uc_catalog.css');
$product_types = module_invoke_all('product_types');

everythings fine now. cheers