Hi,
Right it looks like these books I am having probs with just plain hate me lol. I did what you suggested X by first importing the HTML and then clicking on Tools - ASCII LF -> Word Paragraphs and that put all my carriage returns to line returns. I then selected the whole book and clicked on Clear Formating to get rid of all the text styles and then put it into a Main Text style I created. I then inserted the page breaks.
Now when I export it I get the same error as jopie25. So I have done a screenshot of the error for you:
EDIT: Hmmm seems I have got around that error by putting the HTML into Calibre and then converting it to a txt file and then importing it into BookCreator. And all the page breaks etc are working