I'm having problems getting a reliable share working on an x64 Server 2008 R1 SP1 server.

All works well after a reboot, but after some time (within a day) the shares become unavailable to XP and Server 2003 servers. Interestingly, they remain available to other Server 2008 servers.

On trying to access \\server\share, Server 2003 returns immediately and simply gives me the message "The specified network name is no longer available", XP takes a minute or two to timeout before giving the same message. There doesn't seem to be anything in the event logs indicating a problem.

Doing some googling over the last day or two I've seen the following blamed:

• Bad network drivers ... I've updated to the latest drivers with no result
• Symantec anti-virus ... we're not using it (currently no AV on the server)
• Receive window auto-tuning ... I've disabled with netsh int tcp set global autotuninglevel=disabled and netsh int tcp set global rss=disabled

None of these have had an effect. Windows Firewall is currently disabled.

As other Server 2008 boxes (both x32 and x64) can connect, I can only assume that there's some new security configuration that's not quite right - or there's an AD issue that I need to trace, but don't know where to start. Even if anyone doesn't know how to resolve, if someone knows what I need to look for with Wireshark this would be a help.