W/Stns cannot logon to W2kSvr anymore-beginner/noob problem

Greetings all, love this site and been lurking here for a while as they say, and now my time has come for my debut here... Please be gentle with me, I'm sure I've missed something very very simple!

Since re-introducing internet, the workstations cannot "USE" the server...

Hardware:
So, it's a SOHO LAN, comprising a W2kSvr with an Active Directory/Domain. WinUpdated to latest SP4 etc. (actually...maybe that's...) Old hardware with 256Mb Ram, intel 10/100 NIC, simple basic stuff.

Then there's a P3 with 756Mb Ram on XP sp1. And a std old Sony Laptop - PCG-N505VX on W2k Pro fully updated (I think) Three pc's in total then.

I have internet coming through an ADSL Router/Firewall. It's an Intertex IX66-edflc+PF and it handles all the ADSL and NAT. The Firewall on this is mamouthly strong, and yes, this item is my prode and joy!

The LAN is hardwired with cat5 all linked to an old hub - CNet CN8816TPC-16 port, but the laptop uses a wireless PCMCIA made by AVAYA which links to its equal RG AVAYA base station, which in turn is cat5'd to the hub.

Anti-Virus
Sophos on all machines, AVG7free on the w/stns. Ad-aware is utilized, together with Xoftspy.

Problem:
Users cannot log on to the server!

• The server can be pinged with 100% success.
• The server can be seen under the domain on the XP machine (under My Network Places), but cannot log onto it with ANY member.
• The server and XP machine were working perfectly before the internet was brought back (after a move).
• The Laptop doesn't even get near the domain since it needs to join it, but the reply upon attempting this is that the domain doesn't exist (basically)
• All three machines can ping each other and all have a beautiful internet connection.
• All three have good IP address status, the router is doing its job fine.
• The wireless point came after the logon problem, I don't think the laptop and the wifi have anything to do with the problem at hand.
• If I logon to the XP machine as "Local Machine" only, everything works blindingly fast (well... u know) BUT, if I ask the logon screen to try to connect the the LAN's Domain, it takes 2 - 3 minutes longer to complete the bootup of the PC. Also...
• Once logged onto the PC by making it try to see the domain (upon logging in) Explorer will take anything between 10 seconds and 2 minutes to complete the Explorer screen IF IT HAS TO SHOW THE H: (server) . (In other words, whilst in explorer, anything around the local HDDs is quick, but if the screen moves and the pc needs to make the H: visible, it will take 1 minute to show an H: and all the other things underneath it) Same with any sort of "save as " boxes etc, which obviously, naturally are using explorer.
• DFS is involved on the server, for the H: (This was done since IDE's vol's in NT Server were taken away in W2ksvr!! Grrrrrrr)
• Data on the server would be regretable if lost, but it's not by any means mission critical, but I have no means of backing up this quantity of data.

Any first steps will be welcome, thanks in advance for your time and effort in reading my ebook here! And as I said, I'm sure I need to do something simple, I just need someone to tell me what it is... I've been bashing my head on this for a while now...

N.

 

Does anyone know any good forums where someone might be able to answer this question?