Are you sure the preview mode is also concerned ? Because the "classic" problem here, is when you print, the "Print : Blank records…" is enabled on the Print dialog box.
Also did you check the 'Do not print the selected objects' option ?
To check this, please choose the following menu command : Format > Set Sliding/Printing, just after selecting the concerned objects.
Sorry if my guess are not relevant...
A few other things to check:
Make sure that this happens even if you create a brand new, small test file to rule out any possible issue with your file.
Try changing the font to see if this happens with all fonts, just one, or a group of specific fonts.