I have the following class:

class Prodotti extends SlideshowProPage {
   static $db = array(
      "Prodotto" => "Text",
      "Tipologia" => "Text",
      "Specifiche" => "Text",
      "Caratteristiche" => "HTMLText",
      "Applicazioni" => "HTMLText"
      );
   static $has_one = array(
      "SchedaTecnica" => "File",
      "InfoProdotto" => "File"
      );
   static $has_many = array(
      );   
   
   public function getCMSFields($cms) {
      $fields = parent::getCMSFields($cms);
      $fields->addFieldToTab("Root.Content.Main", new TextField("Prodotto", "Prodotto"), "Content");
      $fields->addFieldToTab("Root.Content.Main", new TextField("Tipologia", "Tipologia"), "Content");
      $fields->addFieldToTab("Root.Content.Main", new TextField("Specifiche", "Specifiche"), "Content");
      $fields->addFieldToTab("Root.Content.Main", new HTMLEditorField("Caratteristiche", "Caratteristiche"), "Content");
      $fields->addFieldToTab("Root.Content.Main", new HTMLEditorField("Applicazioni", "Applicazioni"), "Content");
      $fields->addFieldToTab('Root.Content.Main', new FileIFrameField("SchedaTecnica"), "Content");
      $fields->addFieldToTab('Root.Content.Main', new FileIFrameField("InfoProdotto"), "Content");
      return $fields;
   }   
}

What happens is that when I click on Save all ok, but when I click on "save and publishing" generates "error saving content".
Does anyone know give me an explanation ?
Thanks

Could be many things... Ctrl+Shit+J in chrome/firefox for the console that reports error in more detail...

and without the ?debug, but lokoing at the javascript errors in the console? I'd image it is some SQL error (they usual are for me saving content) and are often solved with a deb/build

Firebug is a good tool for these errors. Ensure your site is running in devmode then try again with Firebugs Console window open, you should see the ajax request and the returned error message.