Can’t activate plugins

I am getting a fatal error on trying to activate 2 different plugins on 2 different blogs. They are in the right place and uploaded to the right place. I have previously successfully activated other plugins on both blogs. The plugins are google analyticator and wordpress automatic update.

The error message is:
Warning: main() [function.main]: open_basedir restriction in effect. File(/wpau_helper.class.php) is not within the allowed path(s): (/var/www/vhosts/sanityplanet.com/httpdocs:/tmp) in /var/www/vhosts/xyz.com/httpdocs/blog/wp-content/plugins/wordpress-automatic-upgrade/wordpress-automatic-upgrade.php on line 134

Warning: main(wpau_helper.class.php) [function.main]: failed to open stream: Operation not permitted in /var/www/vhosts/xyz.com/httpdocs/blog/wp-content/plugins/wordpress-automatic-upgrade/wordpress-automatic-upgrade.php on line 134

Fatal error: main() [function.require]: Failed opening required ‘wpau_helper.class.php’ (include_path=’.:.:’) in /var/www/vhosts/xyz.com/httpdocs/blog/wp-content/plugins/wordpress-automatic-upgrade/wordpress-automatic-upgrade.php on line 134