Hi, me again, I think this is also my problem, last night I measured the output voltage from my PC's serial port and it is only 2.6V, I think my PC might be the problem.
A friend is bringing his computer over this weekend and we are going to try it on his.
Last night we had the mill running nice and smooth but only by constantly moving the mouse while it was running, as soon as I let go of the mouse the steepers slowed down and went all jerky, roll the mouse around on the mouse pad and all is sweet.
To my non computer orientated brain and my friends very computer orientated brain we came to an executive decision that it was the PC and that there is nothing wrong with the rest of the system, it must be the PC.
It was very exciting seeing all 3 axis's moving nice and smooth, so very cool
Thanks to all for your responses.
Will post with results after the weekend.