Download the latest version of WordPress Automatic Upgrade into your wp-content/plugins directory.

Unzip it:

You could try to go to the Plugin page of your WordPress Admin login and start the Automatic upgrade but for me it failed until I changed the file permissions. Go to your wordpress install directory and do:
chmod -R 777 *

Then I started it and gave it the FTP permissions but once more it fails to create some files in wpau-backup. I did:
touch index.php
touch index.html
chmod 777 *

Then I coudl go on to the next step but once more it fails, now to write the backup file. I get:
Task Name: files
Task Description: Backs up all the current files from the wordpress installation
Task Status: Failed
Task Start Date: 2008-08-31 19:38:49
Task End Date: 2008-08-31 19:38:49
Task Log:
Creating files backup archive at
Could not archive the files PCLZIP_ERR_READ_OPEN_FAIL (-2) : Unable to open archive '/web/htmldocs/www/orbblog//wpau-backup/' in wb mode

Go back to the plugin section of the Admin interface and the click “Click Here to Automatically Upgrade WordPress to latest Version.” at the top to start over again. The plugin claims that “Seems you have not completed the clean up process from last upgrade. Please click here to run the clean up process before continuing”. Go on and clean up. Then just follow the steps as they come and all should work just fine.

Once all is done you want to revert file permission, so do:
chmod -R 644 *
find . -type d -exec chmod uog+x {} \;