Start ArcGIS Server Manager locally (on the ArcGIS Server installation machine).
Log In with account (member of local agsadmin users group) which you will later use in WebOffice 10 R3 application respectively project configurations for accessing ArcGIS Server services.

ArcGIS Server Manager login screen
If Log In to ArcGIS Server Manager is successful then this screen should appear:

ArcGIS Server Manager welcome screen
If you are not able to Log In successfully then please check your ArcGIS Server installation, refer to Online Knowledge Base (http://support.esri.com) or contact local Esri support for fixing this problem.