When Firefox loads a page on which a Twitter tweet has been embedded using blockquote, the tweets don't show up. Sometimes I can see them while the page is loading, but they disappear once the page has finished. (Sometimes they don't seem to appear at all.) I'm pretty sure it's not AdBlock that's doing it (I've disabled AdBlock and tried reloading some pages, but the same thing happens), but I don't know what else could be doing it. Has anyone seen anything like this before, and/or does anyone know what's causing it or how to fix it?