In our company, we have a Windows 2003 base WSUS 3.0 with SP2 (Windows Update) server which is responsible to update all local clients and server base windows including 2000 / 2003 / 2008 / XP / W7 versions.
Recently we added four new IBM base servers with Windows 2008 R2 but unable to update, showing following error …
After doing few hours R&D, I found out that this is usually due to the WSUS Update Agent on the client being updated, but the WSUS server itself also needs to be upgraded to then allow communication with the newer agent. After installing SP2, you *MUST* also apply a later update “Update for Windows Server Update Services 3.0 SP2 (KB2720211”
There was no need to reboot the server last time I ran this process, and the clients were able to communicate and obtain updates correctly.