Publisher Defaults off means the nook is generating a user style sheet that does overrides of the body, p and other selectors for fonts, linespacing, margin width and justification, based upon user selection.
This will interact in interesting way depending upon what the style sheet and the xhtml.
I would suggest editing the stylesheet to move moving the font-family attribute to the most general selector possible (body or p if possible), so that it will get overridden cleanly.
Future updates of the Nook Color firmware will 'fix' this by simply ignoring all @font-face rules except for what is specified in the user style, when publisher defaults are off.
Last edited by Jim Lester; 11-02-2011 at 05:44 PM.
Reason: Edited for clarity and helpfulness.