Hi,
With problems like this, it's always helpful to bench test it with a different computer for comparison, preferably one with a built-in serial port. If this is reasonably convenient to do, I would recommend trying this first.
There is an alternate troubleshooting technique using the Hyperterminal program for windows. See here:
http://www.autosportlabs.net/Troublesho ... lt_Lite_Jr.
With the V4 controller be sure to set the baud rate to 38400.
Failing that, I'm sure TriggerWheels would be happy to double-check the unit for you.
Please, let us know what you find out.
Regards,