I’m having a tough time getting the Gcode firmware to work on either the Arduino or the Sanguino. The PDE files compile and upload properly, but when I issue a Gcode command through the serial connection, such as “G1 X10”: it does not work, and I get this crazy response:
Prometheus Fusion Perfection 
Is your baudrate correct? (I had the same error by mixing 9600 bps and something else)
Well, hot damn!
It was on baud rate 9,600, so I tried 19,200… and now I see the proper “start” and “ok” responses. Now to see if it actually works.
Here are the results of some quick tests:
G01 X10 – FAIL
G01 X-10 – success
G01 Y10 – FAIL
G01 Y-10 – success
G01 Z10 – success
G01 Z-10 – success
on the failures, the stepper just jerks a small amount regardless of distance.
Failures:
It seems to me that you are either beyond your software table limit or the software is changing speeds for the positive moves.
Try resetting the software zero of your table position.
plugging the min opto into the max socket on the stepper motor controller fixed this issue.