diff -Naur asterisk-1.6.2.9-orig/apps/app_meetme.c asterisk-1.6.2.9/apps/app_meetme.c
--- asterisk-1.6.2.9-orig/apps/app_meetme.c	2010-05-12 14:03:38.000000000 -0400
+++ asterisk-1.6.2.9/apps/app_meetme.c	2010-06-02 17:21:16.000000000 -0400
@@ -1708,17 +1708,19 @@
 	return 0;
 }
 
-static void conf_queue_dtmf(const struct ast_conference *conf,
+static void conf_queue_dtmf(struct ast_conference *conf,
 	const struct ast_conf_user *sender, struct ast_frame *f)
 {
 	struct ast_conf_user *user;
 
+	ast_mutex_lock(&conf->playlock);
 	AST_LIST_TRAVERSE(&conf->userlist, user, list) {
 		if (user == sender)
 			continue;
 		if (ast_write(user->chan, f) < 0)
 			ast_log(LOG_WARNING, "Error writing frame to channel %s\n", user->chan->name);
 	}
+	ast_mutex_unlock(&conf->playlock);
 }
 
 static void sla_queue_event_full(enum sla_event_type type, 
@@ -3351,7 +3353,9 @@
 			}
 		}
 		/* Remove ourselves from the list */
+		ast_mutex_lock(&conf->playlock);
 		AST_LIST_REMOVE(&conf->userlist, user, list);
+		ast_mutex_unlock(&conf->playlock);
 
 		/* Change any states */
 		if (!conf->users) {