These are the steps I took.

1. Create a server template.
2. Create 2 objects from template.
3. Archived the templates
4. Deleted the templates
5. Final step, purge the templates gives me the following error:

isys_exception_database : Query error: 'DELETE FROM isys_obj WHERE isys_obj__id = '775'': Cannot delete or update a parent row: a foreign key constraint fails (idoit_data/isys_catg_file_list, CONSTRAINT isys_catg_file_list_ibfk_2 FOREIGN KEY (isys_catg_file_list__isys_obj__id) REFERENCES isys_obj (isys_obj__id) ON DELETE NO ACTION ON UPDATE)

This happens on the page:

http://domain/index.php?viewMode=1100&objTypeID=5&objID=774&catgID=31&tvMode=1006&editMode=1#main_content=13

My Idoit data:

System
Operating System UNIX/Linux, Linux OK
PHP Version 5.2.6-1+lenny9 (>5.2.3 recommended) OK
i-doit Code Version 0.9.9-3
i-doit Database Version 0.9.9-3 Revision 6172