Make sure that you are using the corresponding command to the command used to save the picture. GetMedia from a field filled with SetMedia, and GetPicture from SetPicture.
Another reason can be that you have used SetMedia and have from an older version of Director. The media type of Director 6 and 7+ is different from each other and not compatible.
Contact
MMI
36 South Court Sq
Suite 300
Newnan, GA 30263
USA