Just hooked up an old mobo and HDD that I had here and installed Mach and your xml, it seems to be working fine for me.The voltmeter is certainly showing activity when jogging. I will try and hook up a scope to be 100% sure but the probe is at the workshop but should have a bit of coax I can try with.
 Check that you dont have anything that could be hogging the port such as any documents waiting to be printed etc.
Hood

Shouldn't be anything hogging the port seeing That I made this computer a dedicated pc for the machine with a fresh install of windows xp with nothing else.

Just hooked up the scope and it is showing a beautiful pulse, well as beautiul as this clapped out scope can show
 Might be worth a try reinstalling Mach over the top of itself as your xml is certainly fine.
Hood