delete a term from content don't work

Hi,
I have a bug when i try to remove a term from content
if it can help you, see my debug :

my term to remove:

stdClass Object
(
    [tid] => 30
    [vid] => 23
    [name] => Document manquant
    [description] => 
    [weight] => 0
    [language] => 
    [trid] => 0
)

my node object :

stdClass Object
(
    [nid] => 388
    [vid] => 1307
    [uid] => 1
    [created] => 1319490803
    [type] => assurance_decennale
    [language] => fr
    [changed] => 1319493219
    [title] => Assurance RC Décennale
    [revision] => 0
    [revision_moderation] => 0
    [name] => admin
    [date] => 2011-10-24 23:13:23 +0200
    [status] => 1
    [promote] => 1
    [sticky] => 0
    [op] => Enregistrer
    [submit] => Enregistrer
    [preview] => Aperçu
    [delete] => Delete all revisions
    [form_build_id] => form-cfd32909b6c93ae5cca29e21e79e7276
    [form_token] => 77748212dbe6f5b0a920a6d12ffac3fb
    [form_id] => assurance_decennale_node_form
    [menu] => Array
        (
            [mlid] => 0
            [module] => menu
            [hidden] => 0
            [has_children] => 0
            [customized] => 1
            [options] => Array
                (
                    [attributes] => Array
                        (
                            [title] => 
                            [id] => 
                            [name] => 
                            [rel] => 
                            [class] => 
                            [style] => 
                            [target] => 
                            [accesskey] => 
                        )

                )

            [expanded] => 0
            [parent_depth_limit] => 8
            [link_title] => 
            [parent] => primary-links:0
            [weight] => 0
            [plid] => 0
            [menu_name] => primary-links
            [language] => fr
        )

    [path] => document/1319490803
    [pid] => 651
    [pathauto_perform_alias] => 1
    [old_alias] => document/1319490803
    [taxonomy] => Array
        (
            [23] => 30
            [33] => stdClass Object
                (
                    [tid] => 33
                    [vid] => 23
                    [name] => Document à valider par ALG
                    [description] => 
                    [weight] => 3
                    [language] => 
                    [trid] => 0
                )

        )
    [print_display] => 1
    [print_display_comment] => 0
    [print_display_urllist] => 1
    [print_pdf_display] => 1
    [print_pdf_display_comment] => 0
    [print_pdf_display_urllist] => 1
    [notifications_content_disable] => 0
    [teaser] => 
    [format] => 0
    [validated] => 1
    [current_revision_id] => 1307
    [is_current] => 1
    [num_revisions] => 10
    [og_theme] => 
    [is_new] => 
    [body] => 
    [timestamp] => 1319493219
)

I did a patch for resolved ths bug ;) but I found this strange :P
Thx for your help