Joomla! v3.3.6, PHP 5.4.33, Safari(7.1), Chrome(mac 37.0.2062.122)
Created a test user named 'Joe Blow' as user 'jblow' and password 'blowme'.
Subsequent attempt to login returns:
Method Not Implemented
GET to /j301/ not supported.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Once that happens, cannot get into site or admin from same browser. Only recovery is to delete cookies for site. Changing password corrects issue. May be a hosting/site issue, but I don't think so.