After installing this extension,
https://www.magentocommerce.com/magento-connect/product-attachments-extension.html
the login for the administrator doesn't work anymore (see error message at the bottom). Somebody suggested that I disable compilation. If I disable compilation the extension can be installed, but when I re-enable compilation, magento breaks down again, with the same error message.
Thanks in advance!
error report :
: a:5:{i:0;s:75:"Mage registry key "_singleton/fileuploader/observer_product" already exists";i:1;s:2690:"
#0 /home/sel/domains/xxxx/public_html/app/Mage.php(223): Mage::throwException('Mage registry k...')
#1 /home/sel/domains/xxxx/public_html/app/Mage.php(477): Mage::register('_singleton/file...', false)
#2 /home/sel/domains/xxxx/public_html/includes/src/__default.php(21823): Mage::getSingleton('fileuploader/ob...')
#3 /home/sel/domains/xxxx/public_html/app/Mage.php(448): Mage_Core_Model_App->dispatchEvent('core_block_abst...', Array)
#4 /home/sel/domains/xxxx/public_html/includes/src/__default.php(1988): Mage::dispatchEvent('core_block_abst...', Array)
#5 /home/sel/domains/xxxx/public_html/includes/src/__default.php(28232): Mage_Core_Block_Abstract->setLayout(Object(Mage_Core_Model_Layout))
#6 /home/sel/domains/xxxx/public_html/includes/src/__default.php(28248): Mage_Core_Model_Layout->createBlock('adminhtml/page_...', 'head')
#7 /home/sel/domains/xxxx/public_html/includes/src/__default.php(28015): Mage_Core_Model_Layout->addBlock('adminhtml/page_...', 'head')
#8 /home/sel/domains/xxxx/public_html/includes/src/__default.php(27981): Mage_Core_Model_Layout->_generateBlock(Object(Mage_Core_Model_Layout_Element), Object(Mage_Core_Model_Layout_Element))
#9 /home/sel/domains/xxxx/public_html/includes/src/__default.php(27982): Mage_Core_Model_Layout->generateBlocks(Object(Mage_Core_Model_Layout_Element))
#10 /home/sel/domains/xxxx/public_html/includes/src/__default.php(14024): Mage_Core_Model_Layout->generateBlocks()
#11 /home/sel/domains/xxxx/public_html/includes/src/__default.php(13949): Mage_Core_Controller_Varien_Action->generateLayoutBlocks()
#12 /home/sel/domains/xxxx/public_html/includes/src/Mage_Adminhtml_Controller_Action.php(275): Mage_Core_Controller_Varien_Action->loadLayout(NULL, true, true)
#13 /home/sel/domains/xxxx/public_html/app/code/core/Mage/Adminhtml/controllers/IndexController.php(81): Mage_Adminhtml_Controller_Action->loadLayout()
#14 /home/sel/domains/xxxx/public_html/includes/src/__default.php(14098): Mage_Adminhtml_IndexController->loginAction()
#15 /home/sel/domains/xxxx/public_html/includes/src/__default.php(18514): Mage_Core_Controller_Varien_Action->dispatch('login')
#16 /home/sel/domains/xxxx/public_html/includes/src/__default.php(18044): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#17 /home/sel/domains/xxxx/public_html/includes/src/__default.php(20861): Mage_Core_Controller_Varien_Front->dispatch()
#18 /home/sel/domains/xxxx/public_html/app/Mage.php(684): Mage_Core_Model_App->run(Array)
#19 /home/sel/domains/xxxx/public_html/index.php(87): Mage::run('', 'store')
#20 {main}";s:3:"url";s:21:"/index.php/sel-admin/";s:11:"script_name";s:10:"/index.php";s:4:"skin";s:5:"admin";}
