Server Error 500

Hi,

Help since yesterday evening my kayako helpdesk is running in a error and i cannot find the solution.

PHP Fatal error: Call to a member function Get() on a non-object in /var/www/html/__swift/models/Settings/class.SWIFT_Settings.php on line 53

I need my helpdesk back online for my company.

In safari, firefox, opera i get a blanco page in chrome it shows me error 500.
So i check in the logs of apache and get the log above here.

Mysql is running help