applies to Magento 1.5.0.1 installations, for upgrades from Magento 1.5.1.0 please use this article
Symptoms
On attempt to upgrade from Magento 1.5.0.1 to Magento 1.5.1.0 version the following error message is shown by Magento Connect Manager:
CONNECT ERROR: Package 'Mage_All_Latest' is invalid
'./pkginfo/Mage_All_Latest.txt' already exists
Package 'Interface_Adminhtml_Default' is invalid
'./app/design/adminhtml/default/default/layout/admin.xml' already exists
Package 'Interface_Frontend_Default' is invalid
'./app/design/frontend/default/default/etc/widget.xml' already exists
Package 'Interface_Install_Default' is invalid
'./app/design/install/default/default/layout/main.xml' already exists
Package 'Mage_Downloader' is invalid
'./downloader/js/prototype.js' already exists
Package 'Mage_Centinel' is invalid
'./app/code/core/Mage/Centinel/Block/Adminhtml/Validation/Form.php' already exists
Package 'Interface_Frontend_Base_Default' is invalid
'./app/design/frontend/base/default/etc/widget.xml' already exists
Package 'Phoenix_Moneybookers' is invalid
'./app/code/community/Phoenix/Moneybookers/Block/Form.php' already exists
Package 'Find_Feed' is invalid
'./app/code/community/Find/Feed/Block/Adminhtml/Edit/Codes/Edit/Form.php' already exists
Package 'Mage_Compiler' is invalid
'./app/code/core/Mage/Compiler/Block/Process.php' already exists
Package 'Magento_Mobile' is invalid
'./app/code/core/Mage/XmlConnect//Block/Adminhtml/History/Grid.php' already exists
Package 'Mage_Core_Adminhtml' is invalid
'./app/code/core/Mage/Adminhtml/Block/Abstract.php' already exists
Package 'Mage_Core_Modules' is invalid
'./app/code/core/Mage/Admin/Model/Acl/Assert/Ip.php' already exists
Package 'Lib_Js_Ext' is invalid
'./js/extjs/css/README.txt' already exists
Package 'Lib_LinLibertineFont' is invalid
'./lib/LinLibertineFont/Bugs' already exists
Package 'Lib_Js_TinyMCE' is invalid
'./js/tiny_mce/classes/AddOnManager.js' already exists
Package 'Lib_Varien' is invalid
'./lib/Varien/Autoload.php' already exists
Package 'Lib_Google_Checkout' is invalid
'./lib/googlecheckout/googlecart.php' already exists
Package 'Lib_Js_Calendar' is invalid
'./js/calendar/calendar-blue.css' already exists
Package 'Lib_Js_Mage' is invalid
'./js/lib/FABridge.js' already exists
Package 'Lib_Phpseclib' is invalid
'./lib/phpseclib/Crypt/AES.php' already exists
Package 'Mage_Locale_en_US' is invalid
'./app/locale/en_US/Mage_AdminNotification.csv' already exists
Package 'Lib_Mage' is invalid
'./lib/Mage/Archive/Abstract.php' already exists
Package 'Lib_ZF' is invalid
'./lib/Zend/Acl/Assert/Interface.php' already exists
Package 'Lib_Js_Prototype' is invalid
'./js/prototype/debug.js' already exists
Package 'Lib_ZF_Locale' is invalid
'./lib/Zend/Locale/Data/Translation.php' already exists
Cause
The reason is that already installed Magento 1.5.0.1 packages are not registered in the Magento Connect Manager.
Solution
In order to synchronize packages simply unpack set of default files from this archive into var/package folder of your Magento installation and commit changes from Magento Connect Manager (using Commit Changes button) to get packages synchronized. After that the issue should be solved.