Internal Server Error

Hi everyone, I’m brand new to Piwik (inherited it from my predecessor) and unfortunately don’t know a lot about how it works, and I’ve run into an issue where it has started returning 500 Internal Server Error pages when you try to access it, and I haven’t a clue what is wrong. No changes to the server have been made and it’s been running fine for months until now. I’ve tried some basics like recycling the app pool but have still not been able to get the application to respond. Where should I start troubleshooting this?

Windows Server 2008
PHP 5.4.24
No idea how to tell what version of Piwik, though it was just installed a few months ago

Unfortunately software like this (and PHP in general) isn’t my forte so I’m going to need some n00b help to get things running again. Thanks for any advice you can give!

Edit
I should add that the PHP error logs are full of entries like this:
PHP Fatal error: Interface ‘Zend_Db_Statement_Interface’ not found in C:\inetpub\wwwroot\piwik\libs\Zend\Db\Statement.php on line 43
PHP Fatal error: Interface ‘Zend_Db_Statement_Interface’ not found in C:\inetpub\wwwroot\piwik\libs\Zend\Db\Statement.php on line 43
PHP Fatal error: Class ‘Zend_Loader’ not found in C:\inetpub\wwwroot\piwik\libs\Zend\Db\Adapter\Pdo\Abstract.php on line 182
PHP Fatal error: Interface ‘Zend_Db_Statement_Interface’ not found in C:\inetpub\wwwroot\piwik\libs\Zend\Db\Statement.php on line 43
PHP Fatal error: Class ‘Zend_Loader’ not found in C:\inetpub\wwwroot\piwik\libs\Zend\Db\Adapter\Pdo\Abstract.php on line 182
PHP Fatal error: Interface ‘Zend_Db_Statement_Interface’ not found in C:\inetpub\wwwroot\piwik\libs\Zend\Db\Statement.php on line 43
Error in Piwik: Interface ‘Zend_Db_Statement_Interface’ not found

Try reuploading the files of the latest version manually?

Take care to backup your config.ini.php file.

Thanks for your response! So it is as simple as copying the files from a fresh download of Piwik over top of the existing files in C:\inetpub\wwwroot\piwik ? Obviously making sure the config file you mentioned remains safe.

Yep!

Perfect, that plus recycling the app pool did the trick. Thanks!