SBS 2011 and Symantec - clients lost connection to server

Have client with a SBS 2011 Standard, running Exchange and about 15 client computers. All running Symantec Endpoint Protection. THis morning all clients lost connection to server with alert Symantec Endpoint .... The client will block traffic from ip address 192.168.x.x. for the next 600 seconds (ip address of server).
I have ran SEP scans on server and does not catch anything.  How can I troubleshoot this?
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Randy DownsOWNERCommented:
Maybe it's something like this.

... it looks like the problem was the antivirus on the server playing with firewall settings?

If that's the case, your permanent solution was alluded to in your troubleshooting session. Don't install that Symantec AV on the server, or at least don't use anything that inserts a third-party firewall. Use the built-in firewall that is managed by Windows and group policy.

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xav1963Author Commented:
Actually it was a DHCP issue  but thanks for helping out..
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