The Persian font used in facebook (Chrome) suddenly changed today. I don't think it's facebook because

1. Google calendar font seems to have changed too
2. I used to have this problem with 12.10 (currently on 13.04). I resolved it by uninstalling the font facebook was using so that it used the second font in its css font family, which was good.
3. Facebook is still fine on Windows.

So what's going on and what can I do?