I have just bought a CTC 3d printer and I am struggling to get it to finnish a print. I have ran the setup program where you level the bed and load the filament. I have tried a few different models from thingyverse (all with good reviews) and I get the same result. The printer either stops mid process (the fan stays on and I can hear that the motors are still working) or the head will randomly shoot off to one side until stopped by a limit switch. I am using the MakeBot Print software and have it set on Replicator 2 with the balanced print mode. Any idea what I am doing wrong? Is my 3d printer a dud one? I am using the SD card.