I'm using the current version, 9.0.011t.1, and I'm not having the problem. When you say "double-clicking on a book name," you mean "double-clicking on a version name," correct? When I double-click on, say, NIV or BGT or NRS, that becomes the search version without opening a new window.
Check this: go to the Tools menu, then Options. Under General, select Flags, and then in the right pane open Browse Window Configuration Options. See whether Enable automatic secondary Browse Windows is checked. Checking it caused me to get behavior similar to what you've described. Perhaps the configuration gremlins have been at your computer.