After 10.6 Upgrade - XP clients can no longer connect

Question

Just upgraded my server from 10.5 to 10.6.2 and now none of my XP clients can connect via SMB. Can't figure out the issue. They would normally connect via IP on a local network at "\\192.168.80.2", but now nothing happens on the XP side. Just does nothing at all. No login prompts or anything. Anyone know whats going on?
Some stuff from the SMB logs if this helps.
[2009/11/16 10:48:57, 0, pid=1155] /SourceCache/samba/samba-235/samba/source/auth/authodsam.c:opendirectory_smb_pwd_checkntlmv1(387)
opendirectoryuser_auth_and_sessionkey gave -14091 [eDSAuthMethodNotSupported]
[2009/11/16 10:48:57, 0, pid=1155] /SourceCache/samba/samba-235/samba/source/lib/opendirectory.c:getopendirectoryauthenticator(247)
failed to read DomainAdmin credentials, err=67 fd=26 errno=2
[2009/11/16 10:59:12, 1, pid=1155] /SourceCache/samba/samba-235/samba/source/smbd/service.c:close_cnum(1289)
szymon (192.168.80.90) closed connection to service Ledger
[2009/11/16 10:59:12, 1, pid=1155] /SourceCache/samba/samba-235/samba/source/smbd/service.c:close_cnum(1289)
szymon (192.168.80.90) closed connection to service Accounting

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