When I had trouble like this once I was printing to a black and white printer, but I was trying to print in color, so the printer was trying to print with color so all the lines were coming out lighter. I think it had something to do with gray scale, but I can't remember now as this problem happened almost 10 years ago. I will look to see if I can find what I'm thinking of in my current set up, but you might be able to find it before I do.