Intermittent error with Mach3

[Roadkill_321]

Hi, I have been having intermittent errors when I run GCode files.  Right at the start where Mach is given an M3 command, I sometimes get a popup that says Error in Line (Line number) - Unspecified Failure and the program stops.  If I then hit cycle start again the program continues, but does not start the spindle. It doesn't do it all the time, but when it does it I have to restart Mach3, then the problem usually goes away.  Has anyone else had this problem?

I am using version R2.61 of Mach3.

Thanks,
John

[Roadkill_321]

I have since figured out that the error occurs not when the program sends an M3, but when it sends a G20.  

Mach then says "Error in Line 2 - Unspecified failure", Line 2 being where the G20 is.  

It is very annoying   and I would like to resolve this if I can.  Any suggestions?

Thanks John