TPS,
Just a follow up here. I haven't done any "real world" probing today, just some tests, but it appears that the Distance Mode setting is the culprit here. I'm still not really sure why that setting would cause the G31 probing command to move X, Y and Z, instead of just Z, but I'm sure there's a reason, I just haven't found it yet. I'll dig into the manual again, and run some more tests today.
Anyway, thanks for helping solve the problem, I really do appreciate it!
Thanks,
Z