Index: channels/chan_sip.c
===================================================================
--- channels/chan_sip.c	(revision 30626)
+++ channels/chan_sip.c	(working copy)
@@ -1181,7 +1181,8 @@
  				pkt->timer_a = 2 * pkt->timer_a;
  
  			/* For non-invites, a maximum of 4 secs */
- 			siptimer_a = pkt->timer_t1 * pkt->timer_a;	/* Double each time */
+ 			//siptimer_a = pkt->timer_t1 * pkt->timer_a;	/* Double each time */
+			siptimer_a = DEFAULT_RETRANS * pkt->timer_a;
  			if (pkt->method != SIP_INVITE && siptimer_a > 4000)
  				siptimer_a = 4000;
  		
@@ -1214,7 +1215,7 @@
 	}
 	append_history(pkt->owner, "MaxRetries", (ast_test_flag(pkt, FLAG_FATAL)) ? "(Critical)" : "(Non-critical)");
  		
-	pkt->retransid = -1;
+	//pkt->retransid = -1;
 
 	if (ast_test_flag(pkt, FLAG_FATAL)) {
 		while(pkt->owner->owner && ast_mutex_trylock(&pkt->owner->owner->lock)) {
@@ -1251,7 +1252,7 @@
 		pkt = NULL;
 	} else
 		ast_log(LOG_WARNING, "Weird, couldn't find packet owner!\n");
-	if (pkt)
+	if (pkt && pkt->owner)
 		ast_mutex_unlock(&pkt->owner->lock);
 	return 0;
 }
@@ -1277,8 +1278,8 @@
 	pkt->timer_t1 = p->timer_t1;	/* Set SIP timer T1 */
 	if (fatal)
 		ast_set_flag(pkt, FLAG_FATAL);
-	if (pkt->timer_t1)
-		siptimer_a = pkt->timer_t1 * 2;
+	if (pkt->timer_a) 
+ 	    siptimer_a = pkt->timer_a * siptimer_a; 
 
 	/* Schedule retransmission */
 	pkt->retransid = ast_sched_add_variable(sched, siptimer_a, retrans_pkt, pkt, 1);
@@ -1381,8 +1382,9 @@
 			if (cur->retransid > -1) {
 				if (sipdebug && option_debug > 3)
 					ast_log(LOG_DEBUG, "** SIP TIMER: Cancelling retransmit of packet (reply received) Retransid #%d\n", cur->retransid);
-				ast_sched_del(sched, cur->retransid);
+				ast_sched_del_with_lock(sched, cur->retransid); 
 			}
+			cur->retransid = -1; 
 			free(cur);
 			res = 0;
 			break;
@@ -2172,13 +2174,18 @@
 	if (p->initid > -1)
 		ast_sched_del(sched, p->initid);
 
+	ast_mutex_lock(&p->lock);
 	while((cp = p->packets)) {
 		p->packets = p->packets->next;
 		if (cp->retransid > -1) {
-			ast_sched_del(sched, cp->retransid);
-		}
+			ast_sched_del_with_lock(sched, cp->retransid); 
+		} 
+        cp->retransid = -1; 
 		free(cp);
 	}
+
+	ast_mutex_unlock(&p->lock);
+
 	if (p->chanvars) {
 		ast_variables_destroy(p->chanvars);
 		p->chanvars = NULL;
Index: sched.c
===================================================================
--- sched.c	(revision 30626)
+++ sched.c	(working copy)
@@ -60,6 +60,7 @@
 
 struct sched_context {
 	ast_mutex_t lock;
+	ast_mutex_t del_lock; 
 	/* Number of events processed */
 	int eventcnt;
 
@@ -83,6 +84,7 @@
 	if (tmp) {
           	memset(tmp, 0, sizeof(struct sched_context));
 		ast_mutex_init(&tmp->lock);
+		ast_mutex_init(&tmp->del_lock);
 		tmp->eventcnt = 1;
 		tmp->schedcnt = 0;
 		tmp->schedq = NULL;
@@ -302,6 +304,17 @@
 		return 0;
 }
 
+int ast_sched_del_with_lock(struct sched_context *con, int id) 
+{ 
+ 	int res;         
+ 		    
+ 	ast_mutex_lock(&con->del_lock); 
+ 	res = ast_sched_del(con, id); 
+ 	ast_mutex_unlock(&con->del_lock); 
+
+ 	return res; 
+ } 
+
 void ast_sched_dump(const struct sched_context *con)
 {
 	/*
@@ -343,7 +356,9 @@
 	int x=0;
 	int res;
 	DEBUG(ast_log(LOG_DEBUG, "ast_sched_runq()\n"));
-		
+	
+	ast_mutex_lock(&con->del_lock);
+
 	ast_mutex_lock(&con->lock);
 	for(;;) {
 		if (!con->schedq)
@@ -391,6 +406,9 @@
 			break;
 	}
 	ast_mutex_unlock(&con->lock);
+
+	ast_mutex_unlock(&con->del_lock);
+
 	return x;
 }
 
Index: include/asterisk/sched.h
===================================================================
--- include/asterisk/sched.h	(revision 30626)
+++ include/asterisk/sched.h	(working copy)
@@ -102,6 +102,16 @@
  */
 extern int ast_sched_del(struct sched_context *con, int id);
 
+/*! Deletes a scheduled event with sched_del lock */ 
+/*! 
+* \param con scheduling context to delete item from 
+* \param id ID of the scheduled item to delete 
+* Remove this event from being run.  A procedure should not remove its 
+* own event, but return 0 instead. 
+* Returns 0 on success, -1 on failure 
+*/ 
+extern int ast_sched_del_with_lock(struct sched_context *con, int id); 
+
 /*! Determines number of seconds until the next outstanding event to take place */
 /*!
  * \param con context to act upon