text and pictures dissappear after click

This doesn't happen in all the slides. I've checked the transitions and
animations, the master slide and individual slide, and I can't see any
difference or subtlety between the non-functioning slides and others that are
working. And no slides are hidden. On about half the slides in my
presentation, the slide blanks out (showing only the background) after I
click for the last item, either a bullet point or image, when in Slide Show
view. It will not rewind to view the slide as a whole, either, instead
skipping back a couple of slides. The only way I can display the whole slide
contents right now is in the normal view. This is the case consistently for
these slides on any computer I have tried it with, using either Office 2000
or 2007.