Are you scaling the images when you place them? If you select an image, then check either the link info or the Info Panel you will see two numbers for resolution, Actual PPI (the value at the dimensions you chose when the image was saved), and the Effective PPI which is the resolution at the size you are using the image in ID. If you make the image larger, the pixels are getting larger as well.
You will also see pixelation if the links are not up to date.
