http://hpinkjet.sourceforge.net/ have recently released a patch for hplip-0.9.7. It fixes some problems with Photosmart 2570, OJ K550, OJ K850 and DJ9800. Additionally, an overwrite has been fixed in hpiod. The patch can found at http://sourceforge.net/project/showfiles.php?group_id=16846
Thanks, patch is in 0.9.7-r1.