Unfortunately I did all that because it’s in the trouble shooting section of the spec sheet.
Failing that, I changed the COM port numbers to 8 and 9 (they were 10 & 11). That didn’t work either. It’s been suggested Arduino IDE might have issues with com port numbers over 10, so I eliminated that possibility.
Restarted the device, no luck. Restarted XP, no luck. Turned off FIFO buffers, no luck (turned it back on again).
Explored every possible configuration of HyperTerminal, no luck.
Perhaps there new ones only work with Vista 