LarryT,
One thing that I have found is that it is possible to have one serial config in a software program and another in the entry under the serial port entry in Device Manager. This conflict can be the source of the trouble. Your port may not be set up to what you think it is. This may sound strange, but I have seen it occur on more than one machine.
I've not used Crosstalk for a long time, but I find that the old time "Terminal.exe" is very handy for doing serial / ASCII work. It has definable function keys that, once setup, will send your strings with a click of the screen icon. This old program used to be in the early OSs like Win95, etc. but it still works well (currently using it in XP Pro).
Best Regards,
Bob A.