This is due to a modification not being compatible with PHP v5.4x series.
Look in your plugins and search by hook (you can click on "Hook Location" on the top menu/header bar). Search for "login_verify_success" hook: this is the hook located at "functions_login.php #204".
This should help you find the modification that is using that hook location. .
Then check the thread for the "mod" to see if someone has updated it or posted a fix.
Hope this helps