Upgraded automatically, which only worked by changing the index.php file (as WordPress isn't in the root directory but in one named /blogname/) and moving it temporarily to the /blogname/ directory and then moving it back to the root directory.
The update was eventually successful, but now I can't log on to the admin plane (I get a message that I have insufficient rights).
Surprisingly enough, I can still upload new posts with the help of Scribfire software, so I guess the log-in failure is not a fundamental problem).
Thanks in advance for suggestions.
http://wordpress.org/extend/plugins/wordpress-automatic-upgrade/