I get the following error returned when clicking Edit or Add New Customer in Admin >> Customers >> Manage Customers >> "Edit" or "Add New Customer"

Fatal error: Call to undefined method Zend_CodeGenerator_Php_File::shutdown() in /var/app/current/lib/Zend/Log.php on line 366

Lines 363 to 367 highlighted below

{
    /** @var Zend_Log_Writer_Abstract $writer */
    foreach($this->_writers as $writer) {
        $writer->shutdown();
    }

How do I fix this?

We have not experienced this error before and the code within the files indicated in the error has not changed from prior application versions.

I should also add that when trying to Create a New Order on the backend, the Create New Customer button and links to existing customers do not respond when clicked. Not sure if the errors are related but they started at the same time.