I have been getting this error with the last Role Scoper update.
Warning: Call-time pass-by-reference has been deprecated; If you would like to pass it by reference, modify the declaration of [runtime function name](). If you would like to enable call-time pass-by-reference, you can set allow_call_time_pass_reference to true in your INI file in /**/wp-content/plugins/role-scoper/defaults_rs.php on line 518
I have not updated to WP 3.0 yet as I wanted to wait out for bugs and what not. The odd thing is that defaults_rs.php line 518 is blank.
This error prevents people from logging in.