diff --git a/Classes/PHPExcel/Reader/Excel2007.php b/Classes/PHPExcel/Reader/Excel2007.php
index bd91592d..e2a677de 100644
--- a/Classes/PHPExcel/Reader/Excel2007.php
+++ b/Classes/PHPExcel/Reader/Excel2007.php
@@ -1608,15 +1608,16 @@ class PHPExcel_Reader_Excel2007 extends PHPExcel_Reader_Abstract implements PHPE
 											break;
 
 										default:
-											$range = explode('!', (string)$definedName);
-											if (count($range) == 2) {
-												$range[0] = str_replace("''", "'", $range[0]);
-												$range[0] = str_replace("'", "", $range[0]);
-												if ($worksheet = $docSheet->getParent()->getSheetByName($range[0])) {
-													$extractedRange = str_replace('$', '', $range[1]);
-													$scope = $docSheet->getParent()->getSheet((string)$definedName['localSheetId']);
-
-													$excel->addNamedRange( new PHPExcel_NamedRange((string)$definedName['name'], $worksheet, $extractedRange, true, $scope) );
+											if ($mapSheetId[(integer) $definedName['localSheetId']] !== null) {
+												$range = explode('!', (string)$definedName);
+												if (count($range) == 2) {
+													$range[0] = str_replace("''", "'", $range[0]);
+													$range[0] = str_replace("'", "", $range[0]);
+													if ($worksheet = $docSheet->getParent()->getSheetByName($range[0])) {
+														$extractedRange = str_replace('$', '', $range[1]);
+														$scope = $docSheet->getParent()->getSheet($mapSheetId[(integer) $definedName['localSheetId']]);
+														$excel->addNamedRange( new PHPExcel_NamedRange((string)$definedName['name'], $worksheet, $extractedRange, true, $scope) );
+													}
 												}
 											}
 											break;
diff --git a/Classes/PHPExcel/Worksheet.php b/Classes/PHPExcel/Worksheet.php
index fad7c50c..9e65256b 100644
--- a/Classes/PHPExcel/Worksheet.php
+++ b/Classes/PHPExcel/Worksheet.php
@@ -377,9 +377,10 @@ class PHPExcel_Worksheet implements PHPExcel_IComparable
      *
      */
 	public function disconnectCells() {
-        $this->_cellCollection->unsetWorksheetCells();
-        $this->_cellCollection = NULL;
-
+    	if ( $this->_cellCollection !== NULL){
+            $this->_cellCollection->unsetWorksheetCells();
+            $this->_cellCollection = NULL;
+    	}
         //    detach ourself from the workbook, so that it can then delete this worksheet successfully
         $this->_parent = null;
     }
@@ -389,11 +390,10 @@ class PHPExcel_Worksheet implements PHPExcel_IComparable
      *
      */
 	function __destruct() {
-		if ($this->_cellCollection !== NULL) {
-			$this->disconnectCells();
-		}
 		PHPExcel_Calculation::getInstance($this->_parent)
 		    ->clearCalculationCacheForWorksheet($this->_title);
+
+		$this->disconnectCells();
 	}
 
    /**
diff --git a/Examples/12cellProtection.php b/Examples/12cellProtection.php
new file mode 100644
index 00000000..caa38767
--- /dev/null
+++ b/Examples/12cellProtection.php
@@ -0,0 +1,107 @@
+<?php
+/**
+ * PHPExcel
+ *
+ * Copyright (C) 2006 - 2012 PHPExcel
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * @category   PHPExcel
+ * @package    PHPExcel
+ * @copyright  Copyright (c) 2006 - 2012 PHPExcel (http://www.codeplex.com/PHPExcel)
+ * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt	LGPL
+ * @version    ##VERSION##, ##DATE##
+ */
+
+/** Error reporting */
+error_reporting(E_ALL);
+ini_set('display_errors', TRUE);
+ini_set('display_startup_errors', TRUE);
+
+define('EOL',(PHP_SAPI == 'cli') ? PHP_EOL : '<br />');
+
+date_default_timezone_set('Europe/London');
+
+/** Include PHPExcel */
+require_once '../Classes/PHPExcel.php';
+
+
+// Create new PHPExcel object
+echo date('H:i:s') , " Create new PHPExcel object" , EOL;
+$objPHPExcel = new PHPExcel();
+
+// Set document properties
+echo date('H:i:s') , " Set document properties" , EOL;
+$objPHPExcel->getProperties()->setCreator("Mark Baker")
+							 ->setLastModifiedBy("Mark Baker")
+							 ->setTitle("Office 2007 XLSX Test Document")
+							 ->setSubject("Office 2007 XLSX Test Document")
+							 ->setDescription("Test document for Office 2007 XLSX, generated using PHP classes.")
+							 ->setKeywords("office 2007 openxml php")
+							 ->setCategory("Test result file");
+
+
+// Add some data
+echo date('H:i:s') , " Add some data" , EOL;
+$objPHPExcel->setActiveSheetIndex(0);
+$objPHPExcel->getActiveSheet()->setCellValue('A1', 'Crouching');
+$objPHPExcel->getActiveSheet()->setCellValue('B1', 'Tiger');
+$objPHPExcel->getActiveSheet()->setCellValue('A2', 'Hidden');
+$objPHPExcel->getActiveSheet()->setCellValue('B2', 'Dragon');
+
+// Rename worksheet
+echo date('H:i:s') , " Rename worksheet" , EOL;
+$objPHPExcel->getActiveSheet()->setTitle('Simple');
+
+
+// Set document security
+echo date('H:i:s') , " Set cell protection" , EOL;
+
+
+// Set sheet security
+echo date('H:i:s') , " Set sheet security" , EOL;
+$objPHPExcel->getActiveSheet()->getProtection()->setSheet(true);
+$objPHPExcel->getActiveSheet()
+	->getStyle('A2:B2')
+	->getProtection()->setLocked(
+		PHPExcel_Style_Protection::PROTECTION_UNPROTECTED
+	);
+
+
+// Set active sheet index to the first sheet, so Excel opens this as the first sheet
+$objPHPExcel->setActiveSheetIndex(0);
+
+
+// Save Excel 2007 file
+echo date('H:i:s') , " Write to Excel2007 format" , EOL;
+$callStartTime = microtime(true);
+
+$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
+$objWriter->save(str_replace('.php', '.xlsx', __FILE__));
+$callEndTime = microtime(true);
+$callTime = $callEndTime - $callStartTime;
+
+echo date('H:i:s') , " File written to " , str_replace('.php', '.xlsx', pathinfo(__FILE__, PATHINFO_BASENAME)) , EOL;
+echo 'Call time to write Workbook was ' , sprintf('%.4f',$callTime) , " seconds" , EOL;
+// Echo memory usage
+echo date('H:i:s') , ' Current memory usage: ' , (memory_get_usage(true) / 1024 / 1024) , " MB" , EOL;
+
+
+// Echo memory peak usage
+echo date('H:i:s') , " Peak memory usage: " , (memory_get_peak_usage(true) / 1024 / 1024) , " MB" , EOL;
+
+// Echo done
+echo date('H:i:s') , " Done writing file" , EOL;
+echo 'File has been created in ' , getcwd() , EOL;
diff --git a/Examples/runall.php b/Examples/runall.php
index ad37f339..7e97ee82 100644
--- a/Examples/runall.php
+++ b/Examples/runall.php
@@ -52,6 +52,7 @@ $aTests = array(
 	, '10autofilter-selection-2.php'
 	, '11documentsecurity.php'
 	, '11documentsecurity-xls.php'
+	, '12cellProtection.php'
 	, '13calculation.php'
 	, '14excel5.php'
 	, '15datavalidation.php'
diff --git a/changelog.txt b/changelog.txt
index 19364048..a1a6a239 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -52,7 +52,7 @@ Fixed in develop branch for release v1.7.9:
 - Bugfix:   (MBaker)    Work item GH-104 - echo statements in HTML.php
 - Feature:  (Progi1984) Work item GH-8/CP11704 : Conditional formatting in Excel 5 Writer
 - Bugfix:   (MBaker)    Work item GH-113 - canRead() Error for GoogleDocs ODS files: in ODS files from Google Docs there is no mimetype file
-
+- Bugfix:   (MBaker)    Work item GH-80  - "Sheet index is out of bounds." Exception
 
 --------------------------------------------------------------------------------
 BREAKING CHANGE! As part of the planned changes for handling array formulae in