Forbidden errors on dashboard

I just upgraded to 2.2 and when I go to the dashboard, I get the following error:

“You don’t have permission to access /blog/wp-admin/index-extra.php on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request. “

I checked if the file was correctly uploaded and it´s not working. What should I do ?