Muckbeast

Maybe some fellow bloggers can help me out here. My WordPress dashboard says:
WordPress 2.9.1 is available! Please update now.
So I click the link, choose the [Upgrade Automatically] option, and eventually it gets to this:
Downloading update from http://wordpress.org/wordpress-2.9.1.zip.
Unpacking the update.
It churns for a few minutes, and then stops. But it is not upgrading. I’ve always done [...]