Since our upgrade from ArcGIS 10.1 to ArcGIS 10.2, we have been unable to use the "Administer Geodatabase" dialog, The dialog simply does not want to open from ArcCatalog (no response when attempting to open the dialog)
Furthermore, when accessing the Database Properties, I get the following error message, when I press the "Show connected users..." button, : Unable to cast object of type 'System.__ComObject' to type 'ESRI.ArcGIS.DataSourcesGDB.SdeWorkspaceFactoryClass'
What OS are you using? You seem to be using an older version of Windows looking at the screenshots? Are you running the required .NET Framework version?
The Administer Geodatabase dialogs seem to be based on some of the new functionalities of .NET Framework (WPF - Windows Presentation Foundation?) or Windows in 10.2, because the dialogs look markedly different than the "normal" dialogs.
Perhaps important to mention is: That we have two servers with ArcGIS installations, the one runs sql server and the other the arcgis server:
Server 1: Windows Server 2008 R2 Standard sp1, .NET Framework 3.5 sp1. ArcGIS 10.2 for Desktop ArcGIS 10.2 License Manager ArcGIS 10.2 Web Adaptor (IIS) ArcGIS 10.2 for Server ArcGIS 10.2 for Desktop Background Geoprocessing (64-bit)
Server 2: Windows Server Standard sp2, .NET Framework 3.5 sp1. SQL Server 2008 ArcGIS 10.2 for Desktop ArcGIS 10.2 License Manager ArcGIS 10.2 for Microsoft SQL Server ArcSDE 10.2 Command Line Tools
Can you see any problems with our setup? your help would be much appreciated..
Does your Microsoft SQL Server 2008 installation have Service Pack 2 applied? The Esri documentation indicates that the Express, Standard, and Enterprise editions of SQL Server 2008 (non-R2) database are supported at Service Pack 2.
Run the following query against your SQL Server geodatabase to see if SP2 is applied:
Esri does not investigate specific issues or individual requests like this which surface from the forums. You will need to open a ticket with Esri Technical Support if you want that level of assistance for your particular issue. There are many, many reasons why add-ins can cause problems and each occurrence is unique.