Upgrading to  Drupal 7.7 produces a fatal error: What can I do? I have upgraded my local site to Drupal 7.7 from Drupal 7.4, following the instructions in How to upgrade Drupal 7 to Drupal 7.2.

Before I could use update.php, visiting my site got me this message on every page of the site:


  Fatal error: Class 'DatabaseConnection' not found in C:\Users\Developer\Documents\Sites\accountablog\includes\database\database.inc on line 17


Doing a database restore did nothing to alleviate the problem.
What can I do to fix the problem?
The database.inc file does contain the definition of the class DatabaseConnection.

/**
 * Base Database API class.
 *
 * This class provides a Drupal-specific extension of the PDO database
 * abstraction class in PHP. Every database driver implementation must provide a
 * concrete implementation of it to support special handling required by that
 * database.
 *
 * @see http://php.net/manual/en/book.pdo.php
 */
abstract class DatabaseConnection extends PDO {
  // …
}


It is probable the file was not correctly copied, or has been corrupted during the copy; that would explain why the class has not been found, but the class is effectively present in the file that comes with Drupal 7.