If you have changed computers or changed the version of your word processor, this may be the cause.
Last year a friend brought his PAF data file and multimedia folder to my house because his Word 2007 software would not display the photos in the reports. I have Word 97, and in about 10 minutes it had generated a copy of his report with all of the photos. (We saved a copy of the report on his flash drive and he returned home very happy.) If this is your situation, see if a friend has Word 97 (or possibly Word 2000) installed on their computer and would be willing to help you.
If the default photos are shown in your PAF data file, I suspect the word processor as the problem. If the default photos are NOT shown in PAF I suspect the multimedia files need to be relinked. This is normally a quick and easy task if they are all in the same folder.