looks like sometime schemas don't get register correctly but that's not really likely to be a bug of the package shipping the schemas, either due to gconf or to something not going as expected on the machine during the installation
-- Theme schemas corrupted or missing https://launchpad.net/bugs/29061 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
