Users complain that they cannot connect to any network shares on your server. On inspection of the SBS2008 server, you may find you cannot launch Active Directory users and computers, Sites and Services or and other AD tools. Additionally this tends to happen every 7-10 days, but a reboot resolves the issue.
In event Viewer you see 5774 and 5775 errors
Log Name: System
Event ID: 1054
The processing of Group Policy failed. Windows could not obtain the name of a domain controller. This could be caused by a name resolution failure. Verify your Domain Name Sysytem (DNS) is configured and working correctly.
Additioanlly your running Trend Worry Free Business.
The issue is down to Trend Worry free that run a TDI driver. This is being fazed out .
Luckily microsoft have release a patch that resolves this this issue
For more information on this issue please have a read of..