Bugreport: PHP -error in classes.php

On my website http://vale.homelinux.net/wordpress/?cat=2

I get the following error on the sidebar when browsing the categories:

Fatal error: Only variables can be passed by reference in /var/www/wordpress/wp-includes/classes.php on line 629

System information:
http://vale.homelinux.net/phpinfo.php

I am using the latest WP version as well as the WP Gallery2 plugin, on MySQL.

Is this a known bug, or specific to my system?

Thank you for your assistance!