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.
Make a backup of your database
Login your databse via phpMyAdmin
Click SQL
Paste this code in to the Run SQL Query box and click "Go"
UPDATE wp_options SET option_value = '' WHERE option_name = 'active_plugins';