Permissions error

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I am getting afew errors when trying to give a user permissions.

Here it is:

Fatal error: Call to a member function setPermissionObject() on a non-object in /var/www/vhosts/beck.yorserve.co.uk/pickersgillmanorfarm.co.uk/concrete/elements/permission/details/file_set.php on line 7

I can give permissions on some things eg set file properties but not on view files or add files.

Any ideas?