Hello,
Are you using the HiCON Integra?
Try updating your plugin and firmware files to the latest ones. And make sure to use the latest Mach4 build available from their website.
http://www.vitalsystem.com/portal/motion/hicon/hicon_integra/downloads/Here's a short snippet of GCode that you can use to test if the probing is working. And if you can, use a very slow feedrate and try triggering the digitize signal before the probe even touches the table. And remember to keep the EStop button handy.
G0X0Y0Z10
G31 Z-5 F5
Also, make sure that you have the input from the probe mapped to the "Digitize" signal in Mach4. There are other inputs such as "Probe1", "Probe2" and "Probe3", but they're used with different probe commands: G31.1, G31.2, G31.3.
The probe setup should just be standard for Mach4. That is, configure the digitize signal, etc. Aside from that, just wire the digitize signal to the correct input on the HiCON Integra. You may also verify that the digitize signal is correctly configured by triggering the probe manually (even while disarmed), and checking the state in the "Diagnostic" display on the Mach4 screen.
-Marc
Vital System Inc.