If when trying to view the Pixies/Plugin manager, you get a series of error messages about a missing XML function, you will need to check that your installation of PHP includes support for the XML library.
For more information, please consult the PHP manual here:
http://uk.php.net/manual/en/ref.xml.php
If you experience this error on the Pixie/Plugin manager, it doesn't have any effect on the actual operation of the script and you will still be able to use Pixies as normal.