Ive found that if I get a blank page when using smarty it is usually a php error and not a smarty error.
I usually put this snippet of code at the top of a configuration file I use to tell smarty where my directories are
<?php
//error reporting
ini_set('display_errors', '0');
?>
Change the 0 to a 1 to see errors and back to 0 to turn off error reporting.