Airport extreme. XP outlook can no longer connect

Question

Since October My wife and I can no longer connect to our office servers using outlook on PC's via Airport extreme wireless. Both our g5 and g4 have no problems.
The PC's indicate excellent signal and status says "connected "thru our VPN connections to the office.
Both PC's suddenly stopped working this connection thru outlook and the internet.
I noticed many discussion people are in the same boat.
What happened?
Seems odd this is not getting much remedy information.
Sounds widespread.
Are there truly any technical resolutions?
I suspect something in the latest XP updates, CAT login patches etc.
My IT office guy is an amazing craftsman and he could care less about a Mac router.
They ("Windows" OS people) are so sure of themselves...little hope they might suspect there own equipment.

Answer 1

Two things to try:
...Ensure the appropriate NLTM authentication is enabled? Probably NLTMv1.
Server Admin -> Open Directory -> Settings -> Policies -> Authentication
...Ensure that the Microsoft Windows XP clients have a compatible authentication requirement?
This security settings authentication downgrade is set via an msc widget on the higher-budget Microsoft Windows XP variants, or directly via the LMCompatibilityLevel registry knob available within all Windows variants.
With the upper-budget Windows versions, you can run the secpol.msc tool, navigate to Local Policies - Security Options, then to Network Security: LAN Manager authentication level, then (if the box is set this way) switch from "Send NTLMv2 response only" to "Send LM & NTLM - use NTLMv2 session security if negotiated".
On all Windows XP versions including the lower-budget versions, you can use regedit to switch the HKEYLOCALMACHINE\ SYSTEM\ CurrentControlSet\ Control\Lsa registry key value LmCompatibilityLevel to 1