[XeTeX] Strange ligature behaviour

[Gareth Hughes]

Over the last few weeks I've been noticing some strange behaviour in the
formation of ligatures in bold fonts (I don't think it's just restricted
to Libertine-Biolinum). I'm using TeX Live 2009 and have everything
up-to-date, and, somewhere in the update, thing went a little odd.
Ligatures started being replaced by white space or odd glyphs. I've
noticed this in Latin text and Malayalam, and also when updating old
XeTeX documents that displayed perfectly before, but now get all the
ligatures mangled. I wonder if anyone else has experienced this, or
knows what's up. I'll see if I can rustle up a minimal if that would help.

Thanks,

Gareth.