Hello,
"Thumbs up" to Pete's Advice.
There are few things, I see where the issue could be happening..
1) You are using SEP 11.x on the same server which acts as What's Up Gold Server as well. And both are using IIS.
Could you check if they both are install on Default Port 80??
If yes, make sure you install SEPM on a Custom Port 8014
2) Clients are on Workgroup. I don't know if you have check the below documents:
How to install Symantec Endpoint Protection in a workgroup environment
http://www.symantec.com/docs/TECH105662
Best Practices for Central Deployment and Management of Symantec Endpoint Protection (SEP) in a Workgroup environment
3) Check if the Ports used by SEP are Open on both End (Client and Server)
Which Communication Ports does Symantec Endpoint Protection 11.0 use?
In terms of Windows 2008, make sure you have the UAC turned off and proper port exceptions are created in the Windows Firewall OR Turn off the Windows Firewall.
4) Troubleshoot the Communication Issue -
Link provided above by Pete would help you...
Hope that helps!!