I have a Prusa i3 purchased on eBay as a kit. The part I was printing finished successfully, but as soon as it finished, the stepper motor started buzzing very loudly. I tried to home all the axis and the y-axis still wouldn't move and was making the loud buzzing (x,z ok). I turned off the machine, and the motor is completely locked up. I don't see anything external impeding the motor or the belt, it just seized. Any ideas what happened? Not sure why the print was 100% successful and then that happened. This is only my second day using the machine.