need help figuring this MX /A record query problem out

[King, John (Greg) (OAO-HOU)]

Ok im still trying to find out why some systems do this (see debug output
below) and others work just fine. The only difference i can tell is that the
primary that this log refers to is behind a firewall. 

I tried this with 2 other systems offsite (Intel Solaris running Bind 8.2.3)
and it does the same as below but  the A records are kept on the 3rd attempt
to query the mx records for hsc.com. 

So it works outside the network:

try 1 : Succeed
try 2 : fail
try 3 : succeed
try 4... : succeed

But on this one server :

try 1 : Succeed
try 2 : fail 
try 3 .... fail

The following requests get 2 additional answers instead of 4 (additional =
2)

purging the cache fixes it for 1 try then its back to nothing again.

Anyone clue me in here? Could the firewall be doing it or is it local to
this nameserver? If so what and how the heck do i fix it?  Thanks!


> set debug
> set type=mx 
> hsc.com
Server:  myns.dom.ain
Address:  a.a.a.a

;; res_nmkquery(QUERY, hsc.com, IN, MX)
------------
Got answer:
    HEADER:
        opcode = QUERY, id = 51, rcode = NOERROR
        header flags:  response, auth. answer, want recursion, recursion
avail.
        questions = 1,  answers = 2,  authority records = 2,  additional = 4

    QUESTIONS:
        hsc.com, type = MX, class = IN
    ANSWERS:
    ->  hsc.com
        preference = 10, mail exchanger = fw-es09.HAC.com
        ttl = 3600 (1H)
    ->  hsc.com
        preference = 20, mail exchanger = fw-es05.HAC.com
        ttl = 3600 (1H)
    AUTHORITY RECORDS:
    ->  hsc.com
        nameserver = fw-es06.HAC.com
        ttl = 3600 (1H)
    ->  hsc.com
        nameserver = fw-es10.HAC.com
        ttl = 3600 (1H)
    ADDITIONAL RECORDS:
    ->  fw-es09.HAC.com
        internet address = 128.152.1.25
        ttl = 3600 (1H)
    ->  fw-es05.HAC.com
        internet address = 128.152.1.5
        ttl = 3600 (1H)
    ->  fw-es06.HAC.com
        internet address = 128.152.1.6
        ttl = 3600 (1H)
    ->  fw-es10.HAC.com
        internet address = 128.152.1.26
        ttl = 3600 (1H)

------------
hsc.com
        preference = 10, mail exchanger = fw-es09.HAC.com
        ttl = 3600 (1H)
hsc.com
        preference = 20, mail exchanger = fw-es05.HAC.com
        ttl = 3600 (1H)
hsc.com
        nameserver = fw-es06.HAC.com
        ttl = 3600 (1H)
hsc.com
        nameserver = fw-es10.HAC.com
        ttl = 3600 (1H)
fw-es09.HAC.com
        internet address = 128.152.1.25
        ttl = 3600 (1H)
fw-es05.HAC.com
        internet address = 128.152.1.5
        ttl = 3600 (1H)
fw-es06.HAC.com
        internet address = 128.152.1.6
        ttl = 3600 (1H)
fw-es10.HAC.com
        internet address = 128.152.1.26
        ttl = 3600 (1H)
> hsc.com
Server:  myns.dom.ain
Address:  a.a.a.a

;; res_nmkquery(QUERY, hsc.com, IN, MX)
------------
Got answer:
    HEADER:
        opcode = QUERY, id = 52, rcode = NOERROR
        header flags:  response, want recursion, recursion avail.
        questions = 1,  answers = 2,  authority records = 2,  additional = 2

    QUESTIONS:
        hsc.com, type = MX, class = IN
    ANSWERS:
    ->  hsc.com
        preference = 20, mail exchanger = fw-es05.HAC.com
        ttl = 3572 (59m32s)
    ->  hsc.com
        preference = 10, mail exchanger = fw-es09.HAC.com
        ttl = 3572 (59m32s)
    AUTHORITY RECORDS:
    ->  hsc.com
        nameserver = FW-ES06.HAC.com
        ttl = 172772 (1d23h59m32s)
    ->  hsc.com
        nameserver = FW-ES10.HAC.com
        ttl = 172772 (1d23h59m32s)
    ADDITIONAL RECORDS:
    ->  FW-ES06.HAC.com
        internet address = 128.152.1.6
        ttl = 172772 (1d23h59m32s)
    ->  FW-ES10.HAC.com
        internet address = 128.152.1.26
        ttl = 172772 (1d23h59m32s)

------------
Non-authoritative answer:
hsc.com
        preference = 20, mail exchanger = fw-es05.HAC.com
        ttl = 3572 (59m32s)
hsc.com
        preference = 10, mail exchanger = fw-es09.HAC.com
        ttl = 3572 (59m32s)

Authoritative answers can be found from:
hsc.com
        nameserver = FW-ES06.HAC.com
        ttl = 172772 (1d23h59m32s)
hsc.com
        nameserver = FW-ES10.HAC.com
        ttl = 172772 (1d23h59m32s)
FW-ES06.HAC.com
        internet address = 128.152.1.6
        ttl = 172772 (1d23h59m32s)
FW-ES10.HAC.com
        internet address = 128.152.1.26
        ttl = 172772 (1d23h59m32s)
>