Can't save "Display Settings"

When I choose "Display on user profile page" in the User_Visits settings and try to save it, the settings are not saved. Though there is a message that the settings were saved, "Don't display" is chosen after the page has loaded.
Additionally there is an error when I try to access a user profile:

Fatal error: Call to undefined function: array_intersect_key() in /www/htdocs/v074247/html/npower/CMS/drupal-5.7/sites/all/modules/user_visits/user_visits.module on line 282