Index: channels/chan_sip.c
===================================================================
--- channels/chan_sip.c	(revision 152927)
+++ channels/chan_sip.c	(working copy)
@@ -12865,6 +12865,20 @@
 		gettag(req, "To", tag, sizeof(tag));
 		ast_string_field_set(p, theirtag, tag);
 	}
+
+	/* RFC 3261 Section 15 specifies that if we receive a 408 or 481
+	 * in response to a BYE, then we should end the current dialog
+	 * and session. There is no mention in the spec of other 4XX responses,
+	 * but it is known that at least one phone manufacturer potentially
+	 * will send a 404 in response to a BYE, so we'll be liberal in what
+	 * we accept and end the dialog and session if we receive any 4XX 
+	 * response to a BYE.
+	 */
+	if (resp >= 400 && resp < 500 && sipmethod == SIP_BYE) {
+		ast_set_flag(&p->flags[0], SIP_NEEDDESTROY);
+		return;
+	}
+
 	if (p->relatedpeer && p->method == SIP_OPTIONS) {
 		/* We don't really care what the response is, just that it replied back. 
 		   Well, as long as it's not a 100 response...  since we might