diff --git a/openerp/addons/base/res/res_lang.py b/openerp/addons/base/res/res_lang.py
index 3fb58e901f6..3dfc6a5d954 100644
--- a/openerp/addons/base/res/res_lang.py
+++ b/openerp/addons/base/res/res_lang.py
@@ -185,6 +185,10 @@ class lang(osv.osv):
         return grouping, thousands_sep, decimal_point
 
     def write(self, cr, uid, ids, vals, context=None):
+        if 'code' in vals:
+            for rec in self.browse(cr, uid, ids, context):
+                if rec.code != vals['code']:
+                    raise osv.except_osv(_('User Error'), _("Language code cannot be modified."))
         for lang_id in ids :
             self._lang_data_get.clear_cache(self)
         return super(lang, self).write(cr, uid, ids, vals, context)
diff --git a/openerp/osv/orm.py b/openerp/osv/orm.py
index 36e1150c521..71b1103c328 100644
--- a/openerp/osv/orm.py
+++ b/openerp/osv/orm.py
@@ -2527,7 +2527,7 @@ class BaseModel(object):
                 # if val is a many2one, just write the ID
                 if type(val) == tuple:
                     val = val[0]
-                if val is not False:
+                if f._type == 'boolean' or val is not False:
                     cr.execute(update_query, (ss[1](val), key))
 
     def _check_selection_field_value(self, cr, uid, field, value, context=None):
diff --git a/openerp/workflow/instance.py b/openerp/workflow/instance.py
index fd15eee6243..61ad8765124 100644
--- a/openerp/workflow/instance.py
+++ b/openerp/workflow/instance.py
@@ -70,7 +70,12 @@ class WorkflowInstance(object):
         cr = self.session.cr
         cr.execute("select * from wkf_workitem where inst_id=%s", (self.instance['id'],))
         stack = []
-        for work_item_values in cr.dictfetchall():
+        for i, work_item_values in enumerate(cr.dictfetchall()):
+            if i > 0:
+                # test if previous workitem has already processed this one
+                cr.execute("select id from wkf_workitem where id=%s", (work_item_values['id'],))
+                if not cr.fetchone():
+                    continue
             wi = WorkflowItem(self.session, self.record, work_item_values)
             wi.process(signal=signal, force_running=force_running, stack=stack)
             # An action is returned