Check the paragraph styles window to see if you have local overrides on the text (click into it and see if the style name has a + next to it). If so, hold the Option key (Mac OS, possibly the Alt key on Windows) and click the style name. That will clear out local overrides. You can also do it from the fly-out of the styles window.
If you've already tried that, check the character styles window. Character styles will change the look of paragraph styles, but they won't trigger the local overrides + indicator, because they aren't considered a local override. You can apply the None character style if that's what the problem is, but it will only apply to text you have selected, unlike paragraph styles, where all you have to do is click into a paragraph.
Ahuh! It was the Character Styles (I'd tried mucking about with the the Paragraph Styles), importing as out References styles. Thanks very much.
As 'our' rather, need caffeine.