I think I gave you some bad info.
I've never used the plugin, so was going by memory.
Did you use Configure > Config Plugins to enable it, then restart Mach3 and it had it's own menu item (3D Probing)? (Just to make sure it's the right one).
Then, are you using Probe Object with Grid?
That's the one I was talking about.
What version of mach3 are you using?
I saw a post on the Mach forum asking about pausing or stopping the scan, but there were no replies. So, it doesn't appear that you can stop it.
Here's the original thead on it from Art when he wrote it. You might find some help in there.
http://www.machsupport.com/forum/ind...ic,1196.0.html