We have some documents that were causing us the same problem. They were created in Word 2003 and show Black Boxes in place of the pictures in Word 2007. Our trouble is that we also have plans to migrate completely to Office 2007, and if we find more of these types of docs after migration is complete, the option to retrieve the pictures from the Word 2003 doc is not going to be available.
In my experience, "washing" a file though other programs has helped recover lost data a number of times, so, in this case, I tried saving the file in a number of different formats (htm, rtf, and finally saved it as an Adobe PDF) On Saving it as a PDF, the file opened in Acrobat Pro (which I happen to have and use). All the pictures were pictures again, instead of Black Boxes. Then, I Exported from Acrobat Pro to a Word document. When I opened the Word document, all the pictures were back. The only bad thing was that the text wrapping options had changed to "Square" in the Layout options. So, we will have to go back and change those settings.
On a first try at this, I had altered some of the formatting options for one of the pictures (changed size, position, color, set transparent color) and when I saved the file as a PDF, that picture only was still a Black Box. So, the moral of that story is to make no changes to the Black Boxes before "washing" the file through Acrobat Pro. Most of missing images were scans, so I don't know if that makes a difference.
The nice thing about this solution is that you don't still need to have an earlier version of Office to do it. The bad thing is that you do have to have Acrobat Pro.
Just another thing to try to fix your problem. :-)
