I too have FF w/ ABP (I disable it before publishing). I've only added one new plug-in lately - Goodreads Right Click.

Oh, and yes I could see your page break.

I get double line and when I look at the code I see the pagebreak there. But whenever I Save as Draft or Save it disappears (nothing else is missing). If no one else is having a problem, I can just continue to use my work around.

Thanks.