I used to have this problem, but back in December, I came up with an
interesting "cure" for it and haven't had a problem with MS DNS since.
Create a new zone (primary) called "root-servers.net" as if you are
virtually hosting that domain name.
In that new zone, create "A" and "NS" records for the following:
root-servers.net. NS A.root-servers.net
root-servers.net. NS B.root-servers.net
root-servers.net. NS C.root-servers.net
root-servers.net. NS D.root-servers.net
root-servers.net. NS E.root-servers.net
root-servers.net. NS F.root-servers.net
root-servers.net. NS G.root-servers.net
root-servers.net. NS H.root-servers.net
root-servers.net. NS I.root-servers.net
A A 188.8.131.52
B A 184.108.40.206
C A 220.127.116.11
D A 18.104.22.168
E A 22.214.171.124
F A 126.96.36.199
G A 188.8.131.52
H A 184.108.40.206
I A 220.127.116.11
The only other record you will have is the SOA record, which points to you
and has your refresh times in it.
Having this domain "virtually hosted" on your DNS, replaces the same data
that's normally found in the cache area. So if these records disappear out
of the cache again, you still have all of the records in the zone you just
created, so there will be no more problems.
Also, make sure that if you're using Service Pack 2 for NT4, that you've
also installed the DNS hot-fix too (along with any others you may need):
Be sure to change the language from "usa" if you need to.