Okay, after that little hissy fit, and a good night's sleep, I thought I would try another approach, having read the instructions again.
I have previously been following this procedure -
Install Mach3 R3.042.040 to C\:Mach3 and say yes to all - including install LazyCam, which also goes in C\:Mach3.
Update LazyCam with LazyCam 3.01 (including LazyTurn 1.0)
Unzip LazyTurn.exe from LazyTurnMarch7.zip file and copy, and overwrite, into C\:Mach3.
LazyCam operates just fine but LazyTurn comes up with the error message every time, and I've tried it a hundred different ways
So I thought I would try it without Mach3 and in a different directory on a different drive.
Installed LazyCamInstall_301.exe to I\:CNC Stuff\LazyCam
Copied the new LazyTurn.exe file into that directory.
Same result - error message and I can get no further.
I use Mach3 on both a milling machine and a lathe so I know how fantastic the programme is.
I just can't see what I am doing wrong with LazyTurn.
Ross