CNC draw circle problem

HI, I'm using the arduino uno with grbl v0.8c and three L297+L6203 steppermotor drivers. The cnc moves well but it draws 4 quarter circles at the wrong place instead a perfect circle:

http://www.youtube.com/watch?v=E7lyD5JA31M

The gcode is the sample code from github.com

G17 G20 G90 G94 G54
G0 Z0.25
X-0.5 Y0.
Z0.1
G01 Z0. F5.
G02 X0. Y0.5 I0.5 J0. F2.5
X0.5 Y0. I0. J-0.5
X0. Y-0.5 I-0.5 J0.
X-0.5 Y0. I0. J0.5
G01 Z0.1 F5.
G00 X0. Y0. Z0.25

Do someone know this problem ?

Looks like you have one of the steppers wired/configured the wrong way/direction round.
If you know what corner your origin is then move/draw a square and confirm the CNC is drawing correctly compared to the g-code