After asking support to Vectric, they replied that it is known to them and they have a workaround where you have to mod some registry entry for Mach3.
It is understandable that Vectric would not distribute a software patch for another company's product.
Also Artsoft is in the middle of a new version development phase and I would not expect a fix from them any time soon. Especially since this particular problem is not something that directly affects Mach3.
This issue is relevant to both Cut2D and Vcarve Pro. (in fact all Vectric programs) All programs will output gcode directly to a running instance of Mach3.
However a large proportion of users will not have a Vectric CAM program running on their machine control computer at the same time as Mach3. Although I do most of the time.
Also this has nothing to do with what program is listed in the Mach file menu. That is a completely separate issue. Not related at all.
If you know your way around the registry then do a search for entries containing "Mach4.Document". If they are absent then this feature will not work.
It is my experience that Mach3 will make these registry entries on installation to XP, but for some reason, it does not when installing to Win7. Others seem to be reporting that they can be missing on XP as well.
What I did was extract the entries from an XP installation and patch them to my Win7 installation. This is all working perfectly for me.
I have declined to openly share this patch because even though it works for me, it is possible that there may be unintended consequences that I do not understand. I am no programmer.
My advise is, if you know what you are doing with registry edits, then you can easily reproduce what I have done.
And if you do not, then playing around in the registry can have consequences. Wait for an official fix.
Greg