Comment 5 for bug 1277888

This problem is indeed caused by installing GTK 3.10 (from 14.04 or elsewhere).

libgtk-3-0 3.10.6-0ubuntu1~~saucy1 [origin: unknown]

This is the problematic package. Downgrade this package (and other upgraded packages depending on it) to 13.10 packages and the problem is fixed. I don't know if this is a problem with the package itself and also occurs in 14.04 (unlikely) or if it's just the combination of 13.10 and some 14.04 packages.