Thanks for the very good tip which solved my problem. I don't know about everyone else, but, when I start a new project, liking getting this CNC up and running, I tend to verify "simple" things first. So, it was some time before I tried "probing" on my original X Carve but got it working after solving a noise problem.
Then, last year, I upgraded to the X Controller. Didn't have any problems getting it up but waited until now to try probing again. I had been using Charlie's 3 axis Triqueta, but have decided that I need only Z axis probing (for now anyway). Took Charlie's code, already modified by me, and tried just sending the Z axis probe command via UGS. Z stopped immediately with "Probe Error" displayed.
With so many variables like "new controller", "new wiring", "new s/w in the X Controller", "how exactly does the G38 command work", etc., it was hard to know where to start. Probe wiring to X Controller was good. So, with your post here, I first sent a G20 to convert to imperial units. I also reduced the speed to F1 as someone else had suggested (which may not be necessary). I was then able to run G38.2 and short the two probe ends with expected (good) results. Thanks for saving me perhaps a lot of time spinning my wheels! Gary