I am having a problem with grid lines showing up in my print out from autocad, but only in the viewport that has 3D objects in it and displayed in conceptual mode or realistic mode. Don't know what is causing them or how to get rid of them. They do not show up on my screen or in the print preview. They only show up in the final prints and even when printing to a pdf file format. I have printed the same drawing out from other computers that have Autocad 2009 and do not get that problem. My computer has Autocad 2010. I have also uninstalled and reinstalled Autocad but that doesn't work. Anyone got any ideas of what is causing this problem?