Are you perhaps previewing a different record that what you see in browse mode?
When you print from a FileMaker layout, you have key option to specify unique to Filemaker: Records being Browsed or Current Record. When you select the first option, you print all the records in your current found set. When you select the second, you get just the current record.
But when you preview a layout, you have no ability to choose either option. Instead, Preview previews your layout as though 'Records being browsed' is what you will select when printing from the layout. Thus, the data you will see on the screen will be for the first record in your found set and that might not be the record that was current on your layout when you entered preview mode.
While you are in preview mode, you can click the "book control" in the upper left part of the status tool bar and flip through pages of your preview just as it flips you through records when you are in Browse mode.
Thanks ten million. Feeling silly!! That was it exactly.