Why won't my Logitech G27 calibrate properly?

I have just received my Logitech G27 today and I have discovered a calibration issue after less than 30 minutes of use. The wheel itself calibrates when I turn on the PC/PS3 properly but as soon as I have turned it one way, straight forwards is no longer 0 degrees but considerably off centre. The wheel is not even a day old and was not damaged upon set up. Pose advise on why this is happening and how to fix it.