I have experienced quite similar symptom in mid-session on my precise machine, my case is for Japanese characters.
If it happens, `fc-cache -fv` or `unity --replace`` does not recover it, I had to restart X session.
I have this issue after installing xserver-xorg-lts-quantal on precise, and going back to xserver-xorg-lts-precise seems to solve it.
I have experienced quite similar symptom in mid-session on my precise machine, my case is for Japanese characters.
If it happens, `fc-cache -fv` or `unity --replace`` does not recover it, I had to restart X session.
I have this issue after installing xserver- xorg-lts- quantal on precise, and going back to xserver- xorg-lts- precise seems to solve it.