It looks like the font(s) is "Shift Light":
	Code:
	@font-face {
  font-family: "Shift Light";
  font-style: normal;
  font-weight: normal;
  src: url(../fonts/00068.otf);
}
@font-face {
  font-family: "Shift Light";
  font-style: italic;
  font-weight: bold;
  src: url(../fonts/00069.otf);
}
 I don't actually need the fonts.  In the past, I'd automatically delete all the font stuff when I messed with the book.  I only recently started keeping it (I figured there was no down-side to keeping it (except maybe some extra size)).  But, since this might be a new issue with Calibre, I thought I'd report it.
Also, I found another book with fonts (and they're red-shielded as well):  Jim Butcher's "Peace Talks." It has the same problem all around.  Oddly, it too uses those two Shift Light fonts.  So, I'd guess it's an actual Calibre issue.