--- calendar/gui/e-itip-control.c.bug-535459	2008-06-09 18:05:15.000000000 -0400
+++ calendar/gui/e-itip-control.c	2008-06-09 18:05:15.000000000 -0400
@@ -1684,8 +1684,14 @@ e_itip_control_set_data (EItipControl *i
 	priv->top_level = e_cal_util_new_top_level ();
 
 	priv->main_comp = icalparser_parse_string (priv->vcalendar);
-	if (priv->main_comp == NULL) {
+	if (priv->main_comp == NULL || !is_icalcomp_valid (priv->main_comp)) {
 		write_error_html (itip, _("The attachment does not contain a valid calendar message"));
+
+		if (priv->main_comp) {
+			icalcomponent_free (priv->main_comp);
+			priv->main_comp = NULL;
+		}
+
 		return;
 	}
 
--- calendar/gui/itip-utils.c.bug-535459	2008-06-09 18:05:15.000000000 -0400
+++ calendar/gui/itip-utils.c	2008-06-09 18:05:15.000000000 -0400
@@ -1769,3 +1769,26 @@ itip_publish_comp (ECal *client, gchar *
 	return TRUE;
 }
 
+static gboolean
+check_time (const struct icaltimetype tmval, gboolean can_null_time)
+{
+	if (icaltime_is_null_time (tmval))
+		return can_null_time;
+
+	return  icaltime_is_valid_time (tmval) &&
+		tmval.month >= 1 && tmval.month <= 12 &&
+		tmval.day >= 1 && tmval.day <= 31 &&
+		tmval.hour >= 0 && tmval.hour < 24 &&
+		tmval.minute >= 0 && tmval.minute < 60 &&
+		tmval.second >= 0 && tmval.second < 60;
+}
+
+/* returns whether the passed-in icalcomponent is valid or not. It does some sanity checks on values too. */
+gboolean
+is_icalcomp_valid (icalcomponent *icalcomp)
+{
+	return  icalcomp &&
+		icalcomponent_is_valid (icalcomp) &&
+		check_time (icalcomponent_get_dtstart (icalcomp), FALSE) &&
+		check_time (icalcomponent_get_dtend (icalcomp), TRUE);
+}
--- calendar/gui/itip-utils.h.bug-535459	2007-10-12 03:04:17.000000000 -0400
+++ calendar/gui/itip-utils.h	2008-06-09 18:05:15.000000000 -0400
@@ -51,4 +51,6 @@ gboolean itip_publish_begin (ECalCompone
 gboolean reply_to_calendar_comp (ECalComponentItipMethod method, ECalComponent *send_comp,
 				ECal *client, gboolean reply_all, icalcomponent *zones, GSList *attachments_list);
 
+gboolean is_icalcomp_valid (icalcomponent *icalcomp);
+
 #endif
--- plugins/itip-formatter/itip-formatter.c.bug-535459	2007-11-25 21:30:12.000000000 -0500
+++ plugins/itip-formatter/itip-formatter.c	2008-06-09 18:11:26.000000000 -0400
@@ -1360,10 +1360,15 @@ extract_itip_data (FormatItipPObject *pi
 	pitip->top_level = e_cal_util_new_top_level ();
 
 	pitip->main_comp = icalparser_parse_string (pitip->vcalendar);
-	if (pitip->main_comp == NULL) {
+	if (pitip->main_comp == NULL || !is_icalcomp_valid (pitip->main_comp)) {
 		set_itip_error (pitip, container, 
 				_("The calendar attached is not valid"), 
 				_("The message claims to contain a calendar, but the calendar is not a valid iCalendar."));
+		
+		if (pitip->main_comp) {
+			icalcomponent_free (pitip->main_comp);
+			pitip->main_comp = NULL;
+		}
 
 		return FALSE;
 	}