Problem with Cache_Lite

Hello, I try to use Cache_Lite but it does not work as expected. Following Options: cacheDir :: /vat/tmp/ lifeTime :: 120 Code: // Load and set DHTML menu if ( $dhtmlmenu = $cache->get('dhtmlMenu') && $runCodeScript = $cache->get('runCodeScript') ) {

       $page->addScriptDeclaration(  $dhtmlmenu);
       $smarty->assign('topMenuGenScript', $runCodeScript);

print "Cache Used<br />"; } else {

       require 'classes/NavigationMenu.php';
       $menu =& new NavigationMenu();
       $page->addScriptDeclaration( $menu->get() );
       $smarty->assign('topMenuGenScript', $menu->getRunCodeScript() );
       $cache->save( $menu->get(), 'dhtmlmenu');
       $cache->save( $menu->getRunCodeScript(), 'runCodeScript');

print "Cache NOT Used<br />"; } I got always "Cache NOT Used" printed. Does I have something misunderstood? In /vat/tmp/ coes exist some 2 cache files so they got created, Thx in advance. Cheers -Peter