The WPL612 printer can come with an optional 600dpi print head.  When installing the driver, if the listed Wasp WPL612 model is selected the printer will not print properly.  The listed Wasp WPL612 model is intended for the 203dpi print head.

To correct this issue:

Be sure to select the Wasp WPL-644 Printer Model during the 'Specify Printer Model' step of the Wasp Driver Wizard.