[lwip-users] tcpip_thread > switch(msg->type) crash, lwip 1.3.0

[Alan L]

Updated from 1.1.0 to 1.3.0, AT91SAM7X256 port.

Compiles without warnings or errors, but initial debugging the updated code
crashes on the switch(msg->type) after the sys_mbox_fetch call in tcpip_thread.

  LOCK_TCPIP_CORE();
  while (1) {                          /* MAIN Loop */
    sys_mbox_fetch(mbox, (void *)&msg);
    switch (msg->type) {
#if LWIP_NETCONN
    case TCPIP_MSG_API:
...

Even a test direct write to msg->type results in a crash.
msg->type = TCPIP_MSG_API;

My initialization includes...
        tcpip_init( NULL, NULL );

        /* Create the lwIP task.  This uses the lwIP RTOS abstraction layer.*/
        xWebSvrHandle = sys_thread_new("WebSrvr",
                                                                   
vBasicWEBServer,
                                                                   NULL,
                                                                   
lwipBASIC_SERVER_STACK_SIZE,
                                                                   
mainWEBSERVER_PRIORITY);

The mbox and queue seem to be valid.

Any ideas what initialization I'm missing?, what to double-check?
Alan