Understanding reverse DNS better

[Caleb Tennis <caleb.tennis () gmail com>]

We have a /24 from one of our upstream providers that we handoff to a customer.  The /24 has been SWIPd to us, and we 
have nameservers setup with ARIN against that record.

Twice now this information has just "disappeared".  That is, if do reverse DNS lookups, they returns nothing, whereas 
they were just working fine earlier.  If you do an NS lookup on the block, it returns nothing.  The /24 blocks 
immediately surrounding us continue to work just fine.  If we do a lookup directly against our nameserver, it works 
just fine.

It's like the nameserver information against that reverse DNS is just magically gone.

The ARIN record looks good, nothing has changed. Last time, our upstream resubmitted the info so it would repopulate, 
and it started working again soon there after.  I admit to not being the smartest one with how these records work: is 
the problem with the upstream, or ARIN's database, or is there not enough information to tell?

Thanks,
Caleb