Printrbot going off axis when initializing
It is very common that FDM 3D printers "home" their position at the start of each print (as defined by the slicers preprint g-code). This is done by deliberately running the end effector towards its expected X=0, Y=0 position until it hits the endstop switches for each axis. Could it be this behaviour you are seeing? If so, I would suggest checking that your endstops are functioning correctly.

You can manually activate this homing action using the G-code G28 in (for instance) Pronterface. Alternatively, you can verify that your endstops are actually working using the M119-command while pressing each switch manually.