udp socket.create() -> sometimes _callthreadstartex unhandled exception

Hi,

sometimes I get an unhandled exception during the casyncscocket
creation process of my udp socket type...

/* socket.create m_socket */
if(!m_socket.Create(PORT_ARTNET, SOCK_DGRAM, FD_READ))
{
   DWORD err = ::GetLastError();
   ASSERT(target != NULL);
   return FALSE;
}

The exception occur in the sockcore.cpp file (within the
Socket(nSocketType, IEvent) line. I don`t know the meaning of this
exception, but if I go ahead after this exception (without starting
the debugger again) the socket is working....

BOOL CAsyncSocket::Create(UINT nSocketPort, int nSocketType,
    long lEvent, LPCTSTR lpszSocketAddress)
{
    if (Socket(nSocketType, lEvent))
    {
        if (Bind(nSocketPort,lpszSocketAddress))
            return TRUE;
        int nResult = GetLastError();
        Close();
        WSASetLastError(nResult);
    }
    return FALSE;
}

the exact line of the exception if I stop the programm is (return 0) -
in the threadex.c file:

#endif /* defined (_M_CEE) || defined (MRTDLL) */

        _callthreadstartex();

        /*
         * Never executed!
         */
        return(0L);
}

Is my code getting an udp socket correct? or are there any mistakes? I
have to use udp instead of tcp, because the protocol I have to use,
use udp....

best regards
Hans