So, using Control Panel, I uninstalled the Critical Update gizmo from all my machines. It's your choice, but I'd recommend you pass this one by. Some readers are confused about Netscape's offerings. But the 4.5 product is Communicator, not Navigator. They're related, but quite different.
Navigator is the smaller stand-alone browser.
Both Communicator and Navigator have bugs, but they're different products with different versioning. Some readers have asked if BrowserTune collects information from users' browsers or systems. The short answer is no. The tests run entirely within your browser, with nothing collected on the server side. And BT shows this to you in one of the earliest tests so you can see exactly what your browser is telling the world.