New WordPress Version
Up until version 2.7 the easiest way of keeping your WordPress installs up to date has been to install and use the Automatic Upgrade plugin (spmetimes abbreviated to PWAU). With version 2.7 WordPress integrated this functionality into the main script itself so that everyone gets to automatically upgrade without needing to install a plugin to do it.
That leaves a small trap for those who have been using the plugin when it comes to upgrading to version 2.7.1 since the plugin and the built in code conflict with one another. Attempting to upgrade via the link supplied by the plugin incorrectly reports that your installation is already up to date. Trying to upgrade via the built-in process crashes with conflicting functions.
The solution is rather obvious once you realise what is happening. If you first deactivate the plugin the built in upgrade process can then work to upgrade your script even more quickly and easily than the plugin did for upgrading earlier versions.