There’s a great run-down on Drupal.org on how to troubleshoot the dreaded Drupal ‘White Screen of Death’ (WSOD).

This seems to happen every time I add a site to our test server – I find increasing the PHP memory limit to be the fastest way to solve it.

To increase the memory limit assigned to your Drupla install, add this to your /sites/default/settings.php file:

ini_set('memory_limit', '32M');