Hi, Graham
This put me on the right track, your file loaded just fine.
But after working through the editing and save options to use other files, I found the Real Culprit.
I use WordPad text editor from time to time, it has 4 formats for saving files, RTF, TXT, MS- DOS and Unicode, text Document save options.
Mach will load all 4 of them, But the Unicode Txt will not show in G-code Window or View, My default editor for Mach is set to Notepad.
So when I hit Edit "notepad" in Mach, it shows the G-code txt just fine, Mach doesn't completely recognize the Unicode Txt though.
Try this File Below, let me now what you think.
Thanks for the Help, Chip