Printing Excel chart fills area below line whether I ask it to or not

When we try to print some Excel charts with line or scatter graphs on any of our CP2025, CP5225 or Laserjet Pro 400 colour laser printers the print has the area under the line filled with colour and not as a series of lines. The print preview shows the chart without the fill and the chart looks as expected on the screen. Similarly, printing to a pdf or to an non-HP printer gives the required result as does printing from a pdf version of the chart and printing a Word document with the chart pasted in.

Any thoughts?

Thanks

John