[Lynne]

You can also got into debug mode and see what the actual error is.

To enable debug mode edit the /config.php file and change:

$config['debug'] = false;

To:

$config['debug'] = true;

Then edit the /core/includes/config.php file and change:

// $config['Misc']['debug'] = true;

To:

$config['Misc']['debug'] = true;