Time errors with outside NTP server

My environment includes 2 Linux machines in a DMZ that sync time and
provide internal time sync to devices inside our network. My entire 2K3
domain is slaved off of these.


Internal Network/2k3 Servers------->DMZ Linux Time Server-->
Internet---->NIST time source

My 2K servers keep time easily. In moving my domain controllers to 2k3,
I'm getting errors in my system log like this:

Information 38 W32Time The time provider NtpClient cannot reach or is
currently receiving invalid time data from timserver.mydomain.com
(ntp.m|0x0|192.168.1.5:123->xxx.xxx.xxx.xxx:123).


5 minutes later I get an error:

Error 29 W32Time The time provider NtpClient is configured to acquire
time from one or more time sources, however none of the sources are
currently accessible. No attempt to contact a source will be made for 15
minutes. NtpClient has no source of accurate time.

and immediately a warning:

Warning 47 W32Time Time Provider NtpClient: No valid response has been
received from manually configured peer timserver.mydomain.com after 8
attempts to contact it. This peer will be discarded as a time source and
NtpClient will attempt to discover a new peer with this DNS name.

Then about 15 minutes later, everything gets sorted:

Information 37 W32Time The time provider NtpClient is currently
receiving valid time data from timeserver.mydomain.com (ntp.m|0x0|
192.168.1.5:123->xxx.xxx.xxx.xxx:123).

Under 2000, my servers stayed synchronized with no errors or problems.
I have plenty of Linux devices and internal network devices (Cisco,
3Com) that all stay synced without problems.

What is 2k3 doing that is breaking and fixing this? What am I missing?
Thanks!