Could you give us a bit more context here, please?

• 
  
• You have added SQLUM. Are you logging in to Workspace via SQLUM, or via Windows authentication?
  
• I'm assuming you are attempting to add process rights, or K2 server rights, or similar. Are you searching for "domain user", or a specific domain user?
  
• What security label is selected in the search dialog?
  

1. I have added a custom security provider

2. yes i am searching for a domain user

3. the security lable is K2

Dears

Any new updates?

Bashar,
Does it matter where you logon to Workspace (on the server itself versus a workstation)?
Does it matter which user you used to logon to Workspace (service account versus end-user)?
What happens if you do not provide a search string (effectively return all)?
Are there any special characters in the user's name?
Have you tried a different search pattern, such as "Contains" instead of "Starts With"?

I've seen similar issues when the user name started with certain special characters.

Gail