I turned on debugging, and I get this message when I try to create a new account:
Undefined property: stdClass::$defaultpreference_maildisplay in /home/(9my userid)/public_html/(mysite)/user/lib.php on line 77
it gives me several errors, and all about the $default_preference lines in user/lib. I just upgraded to 2.8.3, and this happened. I need help ASAP.