While upgrading from 4.5.8 to 4.6.3 on a Drupal site, the upgrade script stuck and when I refreshed, i got

Fatal error: Cannot redeclare class CRM_Core_ClassLoader in
[MYSITE]/sites/all/modules/civicrm/CRM/Core/ClassLoader.php on line 36

Now I can't even log into the backend of my site.


Can you ensure that you do not have two copies of the civicrm codebase (irrespective of what you might have renamed it to) under


Most likely the error is caused by php finding two copies of the CRM/Core/ClassLoader.php file


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