Today I faced some strange issue. A few weeks ago, we installed a new WSUS Server as replacement for an old one (Windows 2003, 32bit).
All Group Policies were changed in order to point to the new Server, GPOs were updated on all systems, but the following occurred:
So what happened?
Microsoft has released an Update for WSUS 3.0 SP2: KB2720211
The update strengthens the communication channels of the Windows Update Server. The previous Windows Update Server had the update already installed and clients were updated by the server as well.
On the new server, the update was not applied. Therefore the Clients were unable to communicate with WSUS.
After installing the update, everything was working fine again.