Me. I just looked into the code for the reason, and it is a race condition in the logic that determines which panel to delete if you click the box. It just kills the active tab, which may not be switched to yet if you click the close box of an inactive tab. I will work to fix this. For open sourcers, the methods killSearch and killSearchAtIndex should be removed and only a method with a ResultPanel argument should exist to kill a search panel.