Why does a 20mm black line run down scanned copies?

I have just bought a replacement colour and b & w ink for my HP 2575 all in one. When I want to use the scanner to copy and print an image I get a thick black line about 20mm thick running the full width across the middle of the page. I have even tried showing the image on screen prior to printing and it shows on the previews too.
Any ideas please.
Thank you.