If you find youself with a blank admin screen in Wordpress it's probably because of a plugin issue. You can disbale all of your plugins in the database and re-enable them one by one using this method.
1) Make a backup of your database
2) Login your databse via phpMyAdmin
3) Click SQL
4) Paste this code in to the Run SQL Query box and click "Go"
UPDATE wp_options SET option_value = '' WHERE option_name = 'active_plugins';
4) You will see this message if successful. You can now re-enable your plugins one by one.