Sametime fail to open a new chat

Some people in my Sametime list is not working. Everytime when I make a new chat session with the particular people, it will prompt this error message: “There was an error opening a chat session with Diana. Please try again later or contact your system administrator. Reason: 0x80000005”

The rest in my list is working fine, able to chat with.

Subject: Restart Lotus Notes can solve this

When restarted the Lotus Notes, the problem is gone.