Index: /opt/local/apache2/htdocs/Development/TYPO3v4/trunk/typo3/install/index.php
===================================================================
--- /opt/local/apache2/htdocs/Development/TYPO3v4/trunk/typo3/install/index.php	(revision 8082)
+++ /opt/local/apache2/htdocs/Development/TYPO3v4/trunk/typo3/install/index.php	(working copy)
@@ -53,7 +53,7 @@
 $enableInstallToolFile = $PATH_site . '/typo3conf/ENABLE_INSTALL_TOOL';
 
 	// If typo3conf/QUICKSTART is present and can be deleted, automatically create typo3conf/ENABLE_INSTALL_TOOL
-if (is_file($quickstartFile) && unlink($quickstartFile)) {
+if (is_file($quickstartFile) && is_writeable($quickstartFile) && unlink($quickstartFile)) {
 	touch($enableInstallToolFile);
 }