Normally in php when you get a blank page it is because there is an error occurring on the page somewhere and the error reporting is turned off. To see what the error is on these pages add this code to the top of them:
<?php
error_reporting(E_ALL);
ini_set('display_errors','on');
?>
This should let you know why the page is not showing, please post back with the result you get from this and include a copy of the page that is giving you this error and a copy of a blank page that you applied the rule to that is working. I will check on this to see what the problem might be.