Reading back through the posts I couldn't find one that turned on your debug feature.
In the wp-config.php file change
define('WP_DEBUG', false); to
define('WP_DEBUG', true); that will cause WordPress to show error messages.
Make sure you have a copy of this file before changing it.
The next time you get a white screen will you right click on it and then select "view source." Sometimes the screen is white but there is code there.