I actually tried changing in content.opf
Code:
<dc:language>eng</dc:language>
to
Code:
<dc:language>en</dc:language>
and lo and behold, it works. No more bug. How odd. I'll add that extra css to my epubs anyway though, thanks wallcraft.
edit: arrgh, some books work, some don't. i'm just gonna hang my head and skip conversion and hand edit the css myself.