Sounds like you have some sort of transparency (transparent .png ?) on those pages (the white lines are a transparency flattening artifact known as stitching). It's a known problem that ID "emboldens" type on screen when it interacts with transparency, and it often shows in low resolution printing (desktop printers, commercial copiers) as well.
Make sure the text is in front of everything else to minimize the problem, but it probably will not go away. You can add transparency to all pages to make them look the same.