Problem to resolve some addreses

[Martins Purins]

Hi maybe someone can say whats wrong. I have migrate from 8 to 9.1.1 and
all works fine till last month. But now approximately two weeks I can't
resove some hosts
For example
www.aria.com.au
but some after few days (2 or more come back) and resolves fine
For example 
www.linuxhq.com
It not happends very often, but its happen :)
I cant find, where is problem
My soa setting is 
TTL 86400
2001053003 10800 3600 604800 86400.
Or maybe there is problem with hint?
My named.ca
.                  99999999        IN      NS      himmelsborg.dna.lth.se.
                   99999999        IN      NS      NIC.DDN.MIL.
                   99999999        IN      NS      NS.NASA.GOV.
                   99999999        IN      NS      TERP.UMD.EDU.
                   99999999        IN      NS      A.ISI.EDU.
                   99999999        IN      NS      AOS.BRL.MIL.
himmelsborg.dna.lth.se. 99999999        IN      A       130.235.16.11
NIC.DDN.MIL.            99999999        IN      A       10.0.0.51
NIC.DDN.MIL.            99999999        IN      A       26.0.0.73
NS.NASA.GOV.            99999999        IN      A       128.102.16.10
A.ISI.EDU.              99999999        IN      A       26.3.0.103
AOS.BRL.MIL.            99999999        IN      A       128.20.1.2



Martins Purins

t.d. 7034724, 7211003
mob. 9416162
fax. 7222620
e-mail lekters at lanet.lv