1.168.192.inn_addr.arpa

Is the file really so named, with the extra "n", or is that the typo you're looking for?

The "nn" typo aside, what happens if you replace the underscore with a hyphen? Hmmm, later BIND no worky with underscores in domains, true? (Or so I remembered...I think...)
_________________________
Jim


'Tis the exceptional fellow who lies awake at night thinking of his successes.