diff --git a/addons/mass_mailing/wizard/mail_compose_message.py b/addons/mass_mailing/wizard/mail_compose_message.py
index 6c1fc81280e..030ba1f7320 100644
--- a/addons/mass_mailing/wizard/mail_compose_message.py
+++ b/addons/mass_mailing/wizard/mail_compose_message.py
@@ -62,7 +62,8 @@ class MailComposeMessage(models.TransientModel):
                 if mail_values.get('email_to'):
                     recips = tools.email_split(mail_values['email_to'])
                 else:
-                    recips = tools.email_split(partners_email.get(res_id))
+                    partner_id = (mail_values.get('recipient_ids') or [(False, '')])[0][1]
+                    recips = tools.email_split(partners_email.get(partner_id))
                 mail_to = recips[0].lower() if recips else False
                 if (blacklist and mail_to in blacklist) or (seen_list and mail_to in seen_list):
                     # prevent sending to blocked addresses that were included by mistake
diff --git a/addons/website/models/ir_actions.py b/addons/website/models/ir_actions.py
index 176187ea4e0..478972d9a86 100644
--- a/addons/website/models/ir_actions.py
+++ b/addons/website/models/ir_actions.py
@@ -39,7 +39,7 @@ class ServerAction(models.Model):
     def _get_website_url(self):
         for action in self:
             if action.state == 'code' and action.website_published:
-                action.website_url = self._compute_website_url(action.website_path, action.xml_id)
+                action.website_url = action._compute_website_url(action.website_path, action.xml_id)
 
     @api.model
     def _get_eval_context(self, action):
diff --git a/odoo/addons/base/module/module.py b/odoo/addons/base/module/module.py
index 22ae3ca2c58..2b5fe2db583 100644
--- a/odoo/addons/base/module/module.py
+++ b/odoo/addons/base/module/module.py
@@ -16,6 +16,7 @@ from docutils.core import publish_string
 from docutils.transforms import Transform, writer_aux
 from docutils.writers.html4css1 import Writer
 import lxml.html
+import psycopg2
 
 try:
     from cStringIO import StringIO
@@ -479,6 +480,14 @@ class Module(models.Model):
 
     @api.multi
     def _button_immediate_function(self, function):
+        try:
+            # This is done because the installation/uninstallation/upgrade can modify a currently
+            # running cron job and prevent it from finishing, and since the ir_cron table is locked
+            # during execution, the lock won't be released until timeout.
+            self._cr.execute("SELECT * FROM ir_cron FOR UPDATE NOWAIT")
+        except psycopg2.OperationalError:
+            raise UserError(_("The server is busy right now, module operations are not possible at"
+                              " this time, please try again later."))
         function(self)
 
         self._cr.commit()