TAPI with WinModem causing blue screen of death

We have an application that runs on Windows 2000 and higher (TAPI 1.4)
that calls custom hardware data collection devices that are equipped
with modems in order to download the collected data. The "comm/
datamodem" device class is used, and a handle to a serial port
obtained. Standard serial port communication is then performed with
that handle.

If a true, external, serial modem is used, no matter the type of
machine that runs the application, the application works fine.

If a WinModem is used instead of a true serial modem, and the machine
is a uniprocessor, things also are fine.

If a WinModem is used with a machine with more than one core (Intel
Centrino Duo, for instance), the call will be established, some data
will be transferred, but then Windows will blue screen. The blue
screen always identifies the WinModem device driver as the source of
the crash, though the exact address is not always the same from crash
to crash.

Is there anything that can be done from the TAPI side to prevent the
crash? If the device is connected to directly, without using the
modem, the serial communication itself with the device works fine. The
problem only occurs when the data communication is over a modem, and
only when it is a WinModem on a multiprocessor machine.

The above would lead me to believe the WinModem driver is at fault,
but please note that using the exact same hardware with Hyperterminal,
services such as AOL, or with small TAPI test apps which establish
data calls and send data from one side to the other (using the same
TAPI code as our application), do not fail. This leads me to believe
it is something in the interaction with our application with TAPI, but
I can't see an obvious problem.

Is there anything to be aware of when using WinModems? Is there a
recommended way to try to debug what is going on?

Thanks!

Charles
.

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