Paul from D-Link tech support in Australia helped resolve this issue by doing the following:
[My setup is DNS323 FW v1.03 with static IP of 192.168.1.199 and a netbios name of “dns323” going into a WRT54G @ 192.168.1.2. The gateway is set to 192.168.1.2 on the DNS323]

For my XP (SP2) box:
1. Tried accessing the samba shares using \\dns323 after cold boot. No dice. Worked by using the IP of \\192.168.1.199. Paul suggested adding an entry to my hosts or Lmhosts file. I updated the hosts file at: c:\windows\system32\drivers\etc\ with
192.168.1.199 dns323
and then rebooted both the dns323 and my XP box. I could access the dns323 using its UNC path perfectly.


Remark: The firewall ZoneAlarm has blocked the connection, too. After setting the ip-address accordingly to the secure zone the above described steps succeeds. With an additional batch program in the folder autostart
NET USE * \\DNS323\Volume_1 password /USER:name /PERSISTENT:NO
it works automatically fine for each user

For my Vista x64 Ultimate box:
1. Ran secpol.msc. Went to Local Policies, Security Options, Network Security: LAN Manager authentication level. Made sure it was set to Send LM & NTLM - use NTLMv2 session security if negotiated.
2. Rebooted PC and dns323 - could not access dns323 in Vista x64 Ultimate using \\dns323 or \\192.168.1.199
3. Ran compmgmt.msc. Went to Local Users and Groups, Users, Administrator. Unticked “Account in disabled” and clicked Apply then OK. (double-check the admin account is enabled by going back to secpol.msc, Local Policies, Security Options, Accounts: Administrator account status and checking it is enabled.
4. Log out of my standard user account in Vista x64 Ultimate (Start > Log Off), and click on the Admin account (it has no password by default I think). If you've never logged in as Administrator in Vista it will give you a new profile and desktop settings.
5. Tried accessing the dns323 using \\192.168.1.199 and it worked. I had to add an entry to the hosts file like in step 1 in my XP box above. Also copied lmhosts.sam to lmhosts and added the same entry at the bottom before saving and closing (one of these files was read only so I had to make it writable before saving, then switched 'read only' back on afterwards.
6. Rebooted and logged in using Administrator account. \\dns323 was now accessible.

Paul from D-Link Tech Support said the other option is to install a DNS server on your network somewhere and add an entry for the dns323 which has a static ip. He also mentioned some routers have an area where you can enter the IP, MAC Address and sometimes the hostname, (sounds like a built-in dns server on the router to me) but my router doesn't seem to have that feature. (at least with the standard firmware I'm using on the WRT54G!).
Update: 01/18/08: He is probably referring to a feature called static DHCP, which still assigns IP addresses via DHCP, but ensures that each MAC address always gets the same IP. This is typically done by providing a {MAC address, IP address} value pair in static DHCP configuration. Many third-party firmware releases of the popular Linksys WRT54G router (prior to hardware V.5) support static DHCP, for example.

Hope this helps some people - you can email me at sneakers05AToptusnet.com.au if you have any questions. Or ask the guru - Paul!