Mach3 G76 head scratcher

[GeoffV]

Gentlemen

I purchased a licenced copy of Mach3 lathe to drive an Emco c5 which is being upgraded.
Mach3 was downloaded and successfully installed on my office laptop running windows 7 and works correctly including G76 threading canned cycle.
Next I installed Mach3 from the same source onto a Dell OptiPlex 745 PC which is mounted on the Emco C5 and copied the licence file into the mach3 folder. Once installed all appeared correct including the licence's name at the top of the program window, I say all appears correct except that it will not emulate a G76 threading cycle no matter what I do. I have tried reinstalling, copying the XML file from the laptop, hitting it! yet it refuses to read a G76 despite the first part of a test program running normally as far as the G76 line.
Has any one else found this problem or more to the point, a cure?

GeoffV