CNC guy,
Not sure what is causing your problem. Some of the old posts on the Shuttle pro that I looked at mentioned that they had problems that were cured when they re-installed the plug in.
I have had problems getting certain functions to work with the G100. I can select X,Y,Z just fine, and I have a button for home X,Y,Z seperately as well.
Try removing and reinstalling the plug in.
Are you running the G100 or a breakout board?
Monty