Today I lost the ability to see my Windows Server 2008 R2 shares from any of my 3 Windows XP machines in my small office. The 5 Win7 machines haven't been affected (they are still able to browse/access the 2008 server), but none of my WinXP machines can access the 2008R2 server anymore. Yesterday (and for the previous year) everything was working fine. I do not have a domain setup. I can still access Win7 shares from WinXP clients.

Browsing the server logs, I see that the following update was installed last night:

> Installation Ready: The following updates are downloaded and ready for
> installation. This computer is currently scheduled to install these
> updates on ?Thursday, ?November ?15, ?2012 at 3:00 AM: 
> - Security Update for Windows Server 2008 R2 x64 Edition (KB2761226)
> - Security Update for Microsoft .NET Framework 3.5.1 on Windows 7 and Windows Server 2008 R2 SP1 for x64-based Systems (KB2729452)
> - Windows Malicious Software Removal Tool x64 - November 2012 (KB890830)
> - Cumulative Security Update for Internet Explorer 9 for Windows Server 2008 R2 x64 Edition (KB2761451)

It seems likely that something was changed in last night's update, but so far I haven't seen anything on microsoft.com to prove it. I did hear that XP is reaching the end of the road soon. Any ideas?