diff --git a/IPython/frontend/html/notebook/static/js/notebook.js b/IPython/frontend/html/notebook/static/js/notebook.js
index 8ef4e40..e61b909 100644
--- a/IPython/frontend/html/notebook/static/js/notebook.js
+++ b/IPython/frontend/html/notebook/static/js/notebook.js
@@ -762,6 +762,11 @@ var IPython = (function (IPython) {
         // console.log(reply);
         var msg_type = reply.header.msg_type;
         var cell = this.cell_for_msg(reply.parent_header.msg_id);
+        if (!cell){
+            // message not from this notebook
+            console.log("Received IOPub message not caused by one of my cells");
+            return;
+        }
         var output_types = ['stream','display_data','pyout','pyerr'];
         if (output_types.indexOf(msg_type) >= 0) {
             this.handle_output(cell, msg_type, content);
diff --git a/IPython/frontend/qt/base_frontend_mixin.py b/IPython/frontend/qt/base_frontend_mixin.py
index f59fd50..697d45f 100644
--- a/IPython/frontend/qt/base_frontend_mixin.py
+++ b/IPython/frontend/qt/base_frontend_mixin.py
@@ -106,4 +106,9 @@ class BaseFrontendMixin(object):
             from this frontend.
         """
         session = self._kernel_manager.session.session
-        return msg['parent_header']['session'] == session
+        parent = msg['parent_header']
+        if not parent:
+            # if the message has no parent, assume it is meant for all frontends
+            return True
+        else:
+            return parent.get('session') == session
diff --git a/IPython/lib/pylabtools.py b/IPython/lib/pylabtools.py
index 4cda8a5..0b6feb1 100644
--- a/IPython/lib/pylabtools.py
+++ b/IPython/lib/pylabtools.py
@@ -19,6 +19,7 @@ Authors
 # Imports
 #-----------------------------------------------------------------------------
 
+import sys
 from io import BytesIO
 
 from IPython.utils.decorators import flag_calls
@@ -317,6 +318,8 @@ def pylab_activate(user_ns, gui=None, import_all=True, shell=None):
     print """
 Welcome to pylab, a matplotlib-based Python environment [backend: %s].
 For more information, type 'help(pylab)'.""" % backend
+    # flush stdout, just to be safe
+    sys.stdout.flush()
     
     return gui
 
diff --git a/IPython/zmq/kernelapp.py b/IPython/zmq/kernelapp.py
index 9edf871..a8d105e 100644
--- a/IPython/zmq/kernelapp.py
+++ b/IPython/zmq/kernelapp.py
@@ -287,6 +287,10 @@ class KernelApp(BaseIPythonApplication):
         self.write_connection_file()
         self.init_io()
         self.init_kernel()
+        # flush stdout/stderr, so that anything written to these streams during
+        # initialization do not get associated with the first execution request
+        sys.stdout.flush()
+        sys.stderr.flush()
 
     def start(self):
         self.heartbeat.start()