using acrobat pro 9, accessibility report says i need to add alt text, but every image already has alt text.

When I run the accessibility report, it says that there are a number of structure errors that need alt text added to figures, but there are alt text to EVERY figure and even table summaries to every table. It still says I have to add alt text to some figures, although not to all of them, only a small handful. AND when I click on the "No alt text for Figure" error link, sometimes it doesn't take me to the problem, but the other times it takes me to a figure that already has an alt text.

any help would be greatly appreciated!

many thanks in advanced.