Is the record being previewed the same record that was being browsed?
If you have a found set of more than one record, entering preview mode can result in previewing a different record than the current record that was being browsed. Say you are on the 5th record out of 20 in the found set. Preview mode previews the entire set of 20 records starting with the first page of the preview--which may not show the 5th record.
In preview mode, you can click the book control to flip through the previewed pages much like clicking this control flips through reocords when in browse mode.