ErrorCode 0X80070035 : WinXP stopped sharing with Win7...?

I've run into a weird problem that I'm sharing in a hope that someone may have an answer (or a good idea on how to fix)

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Setup:
1 micro desktop (static IP) WinXP Pro and acting as print server, file store, DNLA etc... It also dual boots Ubuntu 12, but by default boots into XP. It's a basic build with very few extra programs installed.

2 laptops + 1 desktop: all Win7 XP Pro (64bit)

All fully MS patched
All running Avast AVTK - free version (no firewall)

They all talk through a GB switch on a common workgroup and users are synced across all machines.
We could share and access drives to and from all machines and everything was working fine.

Nothing new has been installed for months other than Microsoft updates (last one was a few weeks ago)
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Problem:
The desktop PC started dropping offline/crashing and failing to boot with an error "CMOS Checksum Error".
This was easily fixed by replacing the motherboard coin battery and it's had 100% uptime and been error free since then.

But ..... when we try to map to the XP machine we get the 0X80070035 error message come up.

From my machine:
I can see all Win7 and XP machines on the network
I can access all the Win7 shared drives
I click on the XP machine and I can't see what's shared - I get the 80070035 message
When I try to "net use" a share I get "The password or user name is invalid for \\<XPBox>\<share>"
I'm unable to print (the XP machine is the print server which 'Everyone' can print/manage)
I can log into my laptop as the main user of the XP machine (irrelevant, but hey ho)

From the XP machine:
I can see all Win7 and XP machines on the network
I can access all the Win7 shared drives
I can see and access the XP shares through the network
I can log in as any of the laptop users (all users are local admins on all machines)

I've done the following:
Run a full chkdsk on all partitions after replacing the motherboard battery
Ensured the netbios is enabled
Tried stopping the win firewall
Run the Microsoft hotfix for Winsock2 corruption which (sped up the network on the XP machine, but that's all)
Client for Microsoft networks was already activated on all
Checked the XP local policy and network access is allowed
Some shares have 'Everyone' read only access, but they still don't show.


I can still remote-desktop using Dameware and connecting with any of the users/passwords while selecting "Encrypted Windows login"(!?)

It's weird that the XP box can look out and see everything, but the Win7 machines can't look in.

Any help or advise is welcome.

Addendum:
I fired up another XP Pro test system I have in a VirtualMachine and it could connect to the XP desktop.

My laptop can access the Virtual Machine's xp shares too

So it's definately particular to Win7 trying to authenticate with this one XP desktop

The battery changed on the XP desktop - the one I can no longer connect to.

I set it as a static IP as I sometimes run a webserver on it and my router needs to forward ports to a known IP.

Fixed....

I tried re-installing SP3 - no difference

I then remembered that I did a Ghost of my system disk 3 months ago while I was re-jiggling my partitions, so I restored that back - no difference.
It also said it detected new hardware and needed a reboot.

A light went off in my head - it meant that the problem had to be in the bios as that's what passes on the hardwear to the system and it shouldn't have detected anything new. Kicking myself now as it was so obvious when I realised it

I re-set the date in the bios to today (it was still showing Jan 2009)
I set my DVMT mode to fixed
I also set my USB Storage emulation to HardDisk

One of the above fixed it and I'm able to connect again.


Thanks for those that had a look at this oddity
Hopefully it'll help anyone that has something similar in the future :)