samba - Dec 2010 - Windows 7 problem accessing domain member samba server on different subnet

Hi All,

I have a problem accessing Samba 3.0.33 on some CentOS 5 machines on a
different subnet from a Windows 7 computer.

All servers and computers are joined to a Windows 2003 AD domain.

I have identical samba machines on two subnets (CentOS/samba 3.0.33).
The samba machines on the same subnet as my Win 7 computer are
accessible both by the netbios name and ip address.

The samba machines on another subnet are only accessible by IP
address. If I attempt to access these samba servers using their
netbios name, I get prompted for a password.

This configuration has worked for some time, and all CentOS/samba
machines are accessible by Windows XP and 2003 using the netbios name.

I believe Windows 2008 servers have the same issues as Windows 7.
Access can only be made by IP address and not netbios name.

Is this a known issue, or something specific to my environment? I have
been googling this for some time and I cannot find any issue identical
to this.

Some additional info:

security = domain
client use spnego = no
encrypt passwords = yes
ntlm auth = yes
lanman auth = yes
client ntlmv2 auth = yes
remote browse sync = 10.0.0.255 10.0.0.0
remote announce = 10.0.0.255 10.0.0.0
local master = no
wins server = ip of ad wins server

 - Not using winbind but nss_ldap and AD schema extension to support
POSIX attributes.
 - There are no packet filters between subnets.
 - The router is configured to dish out IPv6 addresses, and the
Windows 7 machine has an IPv6 address, as do all the samba/centos
machines. However, the samba/centos machines don't have any AAAA
records, and samba 3.0 does not support IPv6.

I'm fairly stumped. Any tips?

Regards,

Dan