Comment 17 for bug 118593

I've just experienced this, and I was able to fix it. My symptoms were loss of menu icons and the mouse moution_acceleration not working (as well as some other missing gconf values).

The problem is corrupt or missing gconf files. In my case, it was due to a system crash, with a corresponding fsck of my ext2 filesystem (old system) ending up losing some files, but I suppose it could end up happening in many different ways, including unreliable hard drives. Fortunately, there is a way to recover, which I found after much googling.values).

The full solution is here: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=446212

But if you don't care about what the problem is, you just want it fixed, here is what you need to do. As root:
        rm -f /var/lib/gconf/defaults/*
        gconf-schemas --register $(ls /usr/share/gconf/schemas)