When I try to import host items without updating the host itself I uncheck the "Update existing" check box for hosts but leave the item check boxes on. Then when I import the XML, the items are not updated. It seems that the "Hosts" and "Templates" check boxes also affect the "Items" checkbox. They shouldn't, they should only affect the hosts and templates themselves. Even if they are unchecked, we should try to import the other objects, and fail if a host or template is missing.