SQL warnings when synchronizing translations

Hello from Greece,

I am building a site in two languages, English and Greek, with descripions of scientific instruments located in various institutions (Museums etc.).
Instruments and Institutions are content types, with various CCK fields. The "Viewfield" type is also used, to list which instruments are located in a particular institution, when viewing an institution node.

When synchronizing translations between "instrument" nodes, we have the following warnings:

* user warning: You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT nid FROM i18n_node WHERE trid = 11) AND tid IN (SELECT query: DELETE FROM term_node WHERE nid != 35 AND nid IN (SELECT nid FROM i18n_node WHERE trid = 11) AND tid IN (SELECT tid FROM term_data WHERE (language = '' OR language IS NULL) AND vid = 1) in /home/drupal_install/public_html/includes/database.mysql.inc on line 172.

* user warning: You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT nid FROM i18n_node WHERE trid = 11) AND tid IN (SELECT query: DELETE FROM term_node WHERE nid != 35 AND nid IN (SELECT nid FROM i18n_node WHERE trid = 11) AND tid IN (SELECT td.tid FROM term_data td INNER JOIN term_data tt ON td.trid = tt.trid WHERE td.vid = 1 AND td.trid AND tt.language = 'el') in /home/drupal_install/public_html/includes/database.mysql.inc on line 172.

* user warning: Duplicate entry '1-40' for key 1 query: INSERT INTO term_node(tid, nid) SELECT tdt.tid, n.nid FROM i18n_node n , term_data tdt INNER JOIN term_data td ON tdt.trid = td.trid INNER JOIN term_node tn ON tn.tid = td.tid WHERE tdt.trid AND tdt.language = n.language AND n.nid != 35 AND tn.nid = 35 AND n.trid = 11 AND td.vid = 1 in /home/drupal_install/public_html/includes/database.mysql.inc on line 172.

In addition, the viewfields in the "institution" nodes seems to behave randomly: the synchronization often changes the reference to the correct instruments.

Any ideas?

Best wishes, and happy new year,

Yanis