Sounds strange, almost like you have your native units set to mm and have tuned your mtors so that 1 unit instead of moving 1mm actually moves 1 inch.
If you attach your xml I will take a look, would also be handy if you let me know if you have microstepping drives and if so what the amount is and if you have gearing between motor and screw, lastly the pitch of your screws.
Hood