我在Magento（/ admin）的后端部分遇到了问题。它引发了一个错误：
Mage registry key "_singleton/Mage_Core_Model_Domainpolicy" already exists
它会创建一个包含以下内容的报告：
a:5:{i:0;s:74:"Mage registry key "_singleton/Mage_Core_Model_Domainpolicy" already exists";i:1;s:1693:"#0 /home/kfrijters/domains/wijnmaat.nl/public_html/app/Mage.php(224): Mage::throwException('Mage registry k...')
1 /home/kfrijters/domains/wijnmaat.nl/public_html/app/Mage.php(478): Mage::register('_singleton/Mage...', false)
2 /home/kfrijters/domains/wijnmaat.nl/public_html/app/code/core/Mage/Core/Model/App.php(1336): Mage::getSingleton('Mage_Core_Model...')
3 /home/kfrijters/domains/wijnmaat.nl/public_html/app/Mage.php(449): Mage_Core_Model_App->dispatchEvent('controller_acti...', Array)
4 /home/kfrijters/domains/wijnmaat.nl/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(528): Mage::dispatchEvent('controller_acti...', Array)
5 /home/kfrijters/domains/wijnmaat.nl/public_html/app/code/core/Mage/Adminhtml/Controller/Action.php(160): Mage_Core_Controller_Varien_Action->preDispatch()
6 /home/kfrijters/domains/wijnmaat.nl/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(408): Mage_Adminhtml_Controller_Action->preDispatch()
7 /home/kfrijters/domains/wijnmaat.nl/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('login')
8 /home/kfrijters/domains/wijnmaat.nl/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(176): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
9 /home/kfrijters/domains/wijnmaat.nl/public_html/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front->dispatch()
10 /home/kfrijters/domains/wijnmaat.nl/public_html/app/Mage.php(685): Mage_Core_Model_App->run(Array)
11 /home/kfrijters/domains/wijnmaat.nl/public_html/index.php(87): Mage::run('', 'store')
12 {main}";s:3:"url";s:6:"/admin";s:11:"script_name";s:10:"/index.php";s:4:"skin";s:5:"admin";}
有谁知道如何解决这个问题？