When PHP safe_mode is enabled on a server, there are issues with smarty templates in Cerberus. The quick and easy fix for this problem is as follows. Do not make this change unless you need to, as it decreases efficiency (only very slightly though).
Edit the file includes/cerberus-api/templates/templates.php and add a new line directly below the $this->caching line as follows:
$this->debugging = false;
$this->compile_check = true;
$this->caching = false;
$this->use_sub_dirs = false;