Hi,
usually you get this error when the cms.exe is not running of the server which you are trying to connect.
1. Can you verify if you are using the same system name as that of IE when connecting to WEBI RICH CLIENT.?
2. Also please verify if the port number used by CMS is 6400,
You can check this is CCM->SIA->Prpoerties and startup tab on the server
Regards,
RVS