CRM 4.0 Deployment Manager snap-in error

Hi,

I am using CRM 4.0 Version. When i try to open CRM Deployment Manager, i get the snap-in error.

Not sure what could be the reason. I am using the account that installed CRM on the server, it has full control on AD Groups, Sys Admin Role on DB.

Please help me.

Error below:

Unable to cast object of type 'System.DBNull' to type 'System.String'.

at Microsoft.Crm.Admin.AdminService.ConfigDBSecurity.SystemUserData.get_Name()
   at Microsoft.Crm.Tools.Admin.SystemUserNode..ctor(SystemUserData systemUserData)
   at Microsoft.Crm.Tools.Admin.SystemUserListView.OnBuildSubNodes()
   at Microsoft.Crm.Tools.Admin.SystemUserListView.OnInitialize(AsyncStatus status)
   at Microsoft.ManagementConsole.View.ProcessRequest(Request request)
   at Microsoft.ManagementConsole.ViewMessageClient.ProcessRequest(Request request)
   at Microsoft.ManagementConsole.Internal.IMessageClient.ProcessRequest(Request request)
   at Microsoft.ManagementConsole.Executive.RequestStatus.BeginRequest(IMessageClient messageClient, RequestInfo requestInfo)
   at Microsoft.ManagementConsole.Executive.SnapInRequestOperation.ProcessRequest()
   at Microsoft.ManagementConsole.Executive.Operation.OnThreadTransfer(SimpleOperationCallback callback)