Question on 0.0.0.0.in-addr.arpa queries

[Fr34k]

Hi All,

I see the following from many customer devices when snooping DNS queries:

a.client.net -> a.dnsserver.com DNS C 0.0.0.0.in-addr.arpa. Internet PTR ?
a.dnsserver.com -> a.client.net DNS R  Error: 3(Name Error)
a.client.net -> a.dnsserver.com DNS C 0.0.0.0.in-addr.arpa. Internet PTR ?
a.dnsserver.com -> a.client.net DNS R  Error: 3(Name Error)
a.client.net -> a.dnsserver.com DNS C 0.0.0.0.in-addr.arpa. Internet PTR ?
a.dnsserver.com -> a.client.net DNS R  Error: 3(Name Error)
a.client.net -> a.dnsserver.com DNS C 0.0.0.0.in-addr.arpa. Internet PTR ?
a.dnsserver.com -> a.client.net DNS R  Error: 3(Name Error)

Thoughts?
I am seeing this on Solaris with Bind9.4.1-P1

Thank you -- Chris