Is there some case sensitivity involved? After making sure that both A and PTR RR had the same case plus a reload of apache, I am getting the expected output.
Well, the cache key is the hostname/sysname as known by NAV, which ultimately comes from the PTR record for the device's IP address. If you change the casing of the PTR record in DNS, you also effectively invalidate the ipdevinfo DNS cache for that host.
This cache is only in memory, right? Why do I still get this error after apache is restarted? (On a different device than the one I was originally debugging)
--Ingeborg