Jan 14 07:29:41 plato named[23057]: the working directory is not writable
See if that is owned or at least writeable, by named. I vaguely remember running into something similar, and that was the issue--the file wound up being owned by root and not writeable by named.
named does not need write access to /var/named. This has been a "feature" of RH bind packages for a long time.
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