mysql error upon creation of duplicate article on same channel taxonomy

if i create a duplicate article on one and the same republishing taxonomy, i get the following mysql error:

Warning: Duplicate entry '11105' for key 1 query: republish_insert INSERT INTO node_republish (src_nid, rep_nid) VALUES(11105, 14979) in /home/devseed/public_html/e0r/includes/database.mysql.inc on line 120

it should be possible to create a duplicate article on one and the same republishing taxonomy. the user should be informed, that he/she just created a duplicate, though.

alex