A few possibilities include stuff like...
1.) Image is missing and/or not "Linked". Look at whether the image has been moved or taken from a server. The solution is to save the image to a local folder and link to it in the document.
2.) Color space of the document does not match the color space of the image. Make sure the image and the document are appropriate color spaces and they match ( i.e., document = CMYK; image = CMYK ).