First of all, I'm relatively new to CNC, but I've read a lot about many things: screw drives, motors, spindle, controllers, and I've read the whole Mach3Mill Installation and Configuration Manual. I'm a High School student. English is not my mother tongue, so I apologize in advance in case you have any problem understanding what I post.

I have exactly the same problem than stated in this other forum:
http://www.machsupport.com/forum/index.php/topic,17669.0.html
And this video, made by the same person who had that problem, explains my problem very well:
http://www.youtube.com/watch?v=3hUGnM-NUB0

I'm using a 25-pin parallel port cable, a 5-axis breakout board, three two-phase microstepping drivers (CW5045, distributed by Changzhou Chuanwei Motor&Electric) and three NEMA23 stepper motors (bipolar, hybrid). Here is a link to this kit: http://cgi.ebay.com/3-axis-Nema23-stepper-motor-425oz-in-CNC-controller-kit-/300488126022?pt=LH_DefaultDomain_0&hash=item45f67cee46

When beginning to jog or running a Gcode, the motors don't move immediately, but that happens only when first loading Mach3. When I press X+, it moves perfect. Then I press X- and moves very well. Then I press Y+ and there is no problem. When pressing Y- it usually doesn't move at all, there's just a sound like if it wanted to move. Then If I press Z+, it doesn't move. And I've never made my Z axiz move in Z- (reverse).

I have to add that when I press Y-, it kind of "disables" the movement of the X axis. And the problem worsens when I press Z-, because the motors won't move in any direction until I press X+.

If I had to move my motors just in one direction (forward) then I wouldn't have any problem, since they all move forward very well as far as I don't press X-, Y-, or Z- (the problem worsens with Y- and even worse with Z-, as I already said).

I've configured my pins according to my breakout board datasheet. I've checked my wiring a lot of times to see if there's any loose cable or something like that. I've tuned up my motors according to some calculations. I'm pretty sure the problem is not the motor tuning. I have searched this forum many times. Still, I have no idea of what the problem is.

Finally, I've tried to work out this since June 20th up until now, and I can't make it work. CAN SOMEBODY HELP ME PLEASE??? It's a school project and I'm running out of time. I already build the router and I'm just missing this thing!

Try the following:
Go to "Config" --> "Port and Pins" --> check the box "Sherline 1/2 pulse mode".

Restart the program!

Then check each axis under the "Ports and Pins" --> "Motor outputs"
to see if the configuration is ok.

Hope that helps,
John