I looked at the code and a division by zero in Intelli or Optimal placements would indicate that the driver is either reporting a page size of zero or a native driver PPI of zero (something that could never happen in a properly functioning driver).  That can only happen if either the driver or Qimage's stored driver settings are corrupted.  Try holding the shift key when you click the "Properties" button to open the driver, then set all driver settings manually.  Hopefully that will fix any corruption.

Regards,
Mike