I have a Windows Server 2008 R2 installation that is acting as a DC. It has been operational without any problems since late August. All of a sudden, UNC share access experiences an issue where no-one (clients or the DC itself) can access the DC's shares. A reboot of the computer resolves the issue for a minimum time 24-hours, at which time UNC fails again. When this occurs, DNS appears to be fine, routing is fine, I can remote in the server by its FCDN, etc. There are no log entries that really indicate that there is a problem until clients and even the DC itself try to refresh Group Policy, which is accessed via a UNC share.
I realize that details are scant, so if you have any troubleshooting information I can go dig up and post, I would appreciate it.
Best Answer
"Windows Server 2008 network shares may become unresponsive with Symantec Endpoint Protection 11 or Symantec AntiVirus 10.2 client installed and Auto-Protect enabled."
From here.