This has been occurring since 2.9. When I logout I get 'Error 404 - not found'.
I disabled all my plugins.
I rebooted.
I cleared my caches.
It occurs on firefox,IE8,Opera,Chrome.
I regenerated my .htaccess
I resaved permalinks.
It occurs for admin and users.
This occurs on all (6) of my blogs.
I installed a better error trapping and got:
Forbidden. You don't have permission to access /wp-login.php?loggedout=true on this server.
Any ideas?