If you faced with problem that after login to your wordpress blog, dashboard (/wp-admin) is empty, then the most suggestions you will find will be to check extra lines and spaces in wp-config.php and functions.php. First of all try to enable additional logging by setting WP_DEBUG to true in wp-config.php:
It may show the following warnings on wp-login.php page:
Cannot modify header information - headers already sent by (output started at …/wp-config.php:1) in wp-login.php on line xxx
If you tried another suggestions and they didn’t help, try to save wp-config.php in ANSI encoding (regular Windows Notepad allows it). It may be so that it was saved as Unicode and in this case it will have several hidden symbols at beginning, which you won’t be able to remove in most common editors.