Doing some searching via google, shows many people are suffering from memory leaks on heavy array use, you can see the changes of the PHP core here
(sorry could not post url)
You may want to provide some sample code so people can advise/test locally what is failing.
Have you tried checking if anything has changed in your PHP setup with a phpinfo.php page with
PHP Code:
<?php phpinfo();?>
inside.
You can also try putting errors on in php.ini or via .htaccess.
When you get a white page straight away it usally means a code error has taken place so seeing the code could route out the problem. Just because you are using similar code else where and it works, doesnt mean this version does. You could have a rogue .,'" etc etc.