After upgrading to 2.1 the main settings page here is just a white page: /wp-admin/admin.php?page=all-in-one-seo-pack/aioseop_class.php
Looking at logs, here is the error message:
PHP Fatal error: Cannot redeclare class OAuthException in /usr/share/php/OAuth.php on line 8
I guess this is b/c the update comes with the OAuth library but doesn't first check that it's already installed on the server? Hopefully it's a quick fix for the developer.