Index: t3lib/class.t3lib_befunc.php
===================================================================
--- t3lib/class.t3lib_befunc.php	(revision 3058)
+++ t3lib/class.t3lib_befunc.php	(working copy)
@@ -3969,5 +3969,32 @@
 		}
 		return array('rows'=>$theRows,'list'=>$out);
 	}
+	
+	/**
+	 * Returns the name of the backend script relative to the TYPO3 main directory.
+	 *
+	 * @param	string		Optional name of the backend interface. If no interface is given, the interface for the current backend user is used.
+	 * @return	string
+	 */
+	public static function getBackendScript($interface = '') {
+		if(!$interface) {
+			$interface = $GLOBALS['BE_USER']->uc['interfaceSetup'];
+		}
+		
+		switch($interface) {
+			case 'backend_old':
+				$script = 'alt_main.php';
+				break;
+			case 'frontend':
+				$script = '../.';
+				break;
+			case 'backend':
+			default:
+				$script = 'backend.php';
+				break;
+		}
+		
+		return $script;
+	}
 }
 ?>
Index: t3lib/class.t3lib_tsfebeuserauth.php
===================================================================
--- t3lib/class.t3lib_tsfebeuserauth.php	(revision 3058)
+++ t3lib/class.t3lib_tsfebeuserauth.php	(working copy)
@@ -429,7 +429,7 @@
 							parent.opener.top.goToModule("'.$pageModule.'");
 							parent.opener.top.focus();
 						} else {
-							vHWin=window.open(\''.TYPO3_mainDir.'alt_main.php\',\''.md5('Typo3Backend-'.$GLOBALS['TYPO3_CONF_VARS']['SYS']['sitename']).'\',\'status=1,menubar=1,scrollbars=1,resizable=1\');
+							vHWin=window.open(\''.TYPO3_mainDir.t3lib_BEfunc::getBackendInterface().'\',\''.md5('Typo3Backend-'.$GLOBALS['TYPO3_CONF_VARS']['SYS']['sitename']).'\',\'status=1,menubar=1,scrollbars=1,resizable=1\');
 							vHWin.focus();
 						}
 						return false;
Index: t3lib/class.t3lib_userauth.php
===================================================================
--- t3lib/class.t3lib_userauth.php	(revision 3058)
+++ t3lib/class.t3lib_userauth.php	(working copy)
@@ -551,9 +551,10 @@
 
 			if($GLOBALS['TYPO3_CONF_VARS']['BE']['lockSSL'] == 3 && $this->user_table == 'be_users')	{
 				$requestStr = substr(t3lib_div::getIndpEnv('TYPO3_REQUEST_SCRIPT'), strlen(t3lib_div::getIndpEnv('TYPO3_SITE_URL').TYPO3_mainDir));
-				if($requestStr == 'alt_main.php' && t3lib_div::getIndpEnv('TYPO3_SSL'))	{
+				$backendScript = t3lib_BEfunc::getBackendScript();
+				if($requestStr == $backendScript && t3lib_div::getIndpEnv('TYPO3_SSL'))	{
 					list(,$url) = explode('://',t3lib_div::getIndpEnv('TYPO3_SITE_URL'),2);
-					header('Location: http://'.$url.TYPO3_mainDir.'alt_main.php');
+					header('Location: http://'.$url.TYPO3_mainDir.$backendScript);
 					exit;
 				}
 			}
Index: typo3/alt_shortcut.php
===================================================================
--- typo3/alt_shortcut.php	(revision 3058)
+++ typo3/alt_shortcut.php	(working copy)
@@ -677,7 +677,7 @@
 			// Changing workspace and if so, reloading entire backend:
 		if (strlen($this->changeWorkspace))	{
 			$BE_USER->setWorkspace($this->changeWorkspace);
-			return $this->doc->wrapScriptTags('top.location.href="alt_main.php";');
+			return $this->doc->wrapScriptTags('top.location.href="'. t3lib_BEfunc::getBackendScript() . '";');
 		}
 			// Changing workspace and if so, reloading entire backend:
 		if (strlen($this->changeWorkspacePreview))	{
Index: typo3/mod/user/ws/index.php
===================================================================
--- typo3/mod/user/ws/index.php	(revision 3058)
+++ typo3/mod/user/ws/index.php	(working copy)
@@ -306,7 +306,7 @@
 		if ($changeWorkspace != '') {
 			$BE_USER->setWorkspace($changeWorkspace);
 			$this->content = $this->doc->startPage($LANG->getLL('title'));
-			$this->content .= $this->doc->wrapScriptTags('top.location.href="' . $BACK_PATH . 'alt_main.php";');
+			$this->content .= $this->doc->wrapScriptTags('top.location.href="' . $BACK_PATH . t3lib_BEfunc::getBackendScript() . '";');
 		}
 		else {
 				// Starting page: