Accepted chats not opening chat window

When a user signs onto to the chat through the web interface, the notification pops up on the agent’'s side. However, when the agent clicks ‘‘Accept’’ the notification goes away, and no window pops up to allow the agent to address the client. The window will only pop up if the client enters something first. This problem existed in 2.5.1 and after an upgrade still exists in 2.5.2. Any suggestions?