Following initial set up of WSUS I immediately hit a update error on the already updated clients, namely WSUS client error 800B0001.

Fix WSUS client error 800B0001

To fix this error you’ll need to apply a patch to the server – kb2720211.

For x86 servers visit http://www.microsoft.com/en-us/download/details.aspx?id=29998

For x64 servers visit  http://www.microsoft.com/en-us/download/details.aspx?id=29999