blank white page in admin, white space hunting?

What your seeing is probably a PHP fatal error, however your server will be configured to log them to the error log rather than present it on the frontend.

To find out what the error is, check your error log, or alternatively, if you don’t have access to the error log or enabling the error log is not an option, you could enable printing the errors to the frontend. This will give you a blank page but now there will be a PHP error message. You will not want to do this in a production environment, and you won’t want to enable this for very long if you’re forced into that situation.

One way of doing this is by enabling WP_DEBUG in wp-config.php. How you would enable error logging to the screen is a subject for another question